Of the nine copper plates, eight show imagery and detail quite similar to seals or tablets excavated from major Indus Valley sites such as Mohenjo-daro, Harappa and Chanhudaro. In most cases, the similarity with respect to detail is striking (Figure 9).

The most unusual of the copper plates are Plates 1 and 2 which depict a figure or deity with a horned head-dress. No seal is known that is overall comparable to Plate 1 (Figure 10), which depicts a naked figure, wearing a horned head-dress, seated in a yogic position, and bearing a star or gem symbol on his chest, perhaps antecedent to the jewel Kaustubha worn by Vishnu (S. Chandrasekhar, pers. comm.). At the right of the figure is a small plant. Seals with plants are very rare and Sharma (2011; p. 168) notes that only 12 seals are known showing a plant, which is usually the pipal or sacred fig (Ficus religiosa). The plant here is a herb with a taproot, long leaves and two flowers. However, the pipal is a large tree with cordate mucronate leaves (see Plate 5) and relatively insignificant cauliflorous flowers. Thus the plant depicted may be something like tulasi (Ocimum tenuiflorum), a holy plant often associated with Vishnu (Gupta, 2001; p. 54), a poppy4, or Indian ginseng (Withania somnifera). At the left of the plate is a crudely depicted cult object, perhaps a ceremonial vessel, or part thereof, that may be incomplete due to the size of the text. Until recent years, the figure itself seemed atypical of deity representation; however, a bifacial terracotta tablet found by Meadow and Kenoyer in 1994 at Harappa shows a very similar figure (Meadow and Kenoyer, 1997; Kenoyer, 1998; p. 114).

The deity depicted on Plate 2 is more conventional, and several roughly similar figures are known from iconic seals. The figure wears an elaborate bovine head-dress or mask that seems to have an upper projecting pipal branch. His long hair appears as a braided mass that falls to the left, and both arms bear large bangles. On seals, this type of figure is often accompanied by fig branches, and thus he is sometimes known as the “fig deity”. As with Plate 1, a nearly identical image appears on one of the four rectangular faces of small molded terracotta tablets found by Meadow and Kenoyer in 1994 at Harappa.

Plates 3 and 4 bear only large Indus script characters, and no identical seals or tablets are known; however, it is worth noting that an elongate steatite seal from Mohenjo-daro, bearing only characters, has five of its six characters similarly inscribed and in common with Plate 3.

Plates 5 to 9 bear animal images seen on steatite seals. Plate 5 bears a horned tiger, an image comparatively rare on steatite seals, but found on Mohenjo-daro copper tablets. The combination of forms of two powerful animals, the head of a bull and the body of a tiger, likely represented even greater power and/or protection. Whereas seals depicting bulls and even the rhinoceros often provide an altar or trough below the animal’s head, here the horned tiger is given a pipal leaf, a sacred symbol.

Plate 6 bears a stately zebu bull, and such images are well known from steatite seals. The zebu bull seals are not as common as the “unicorn” or single horned bull seals, and tend to be relatively large seals and often very beautifully and finely engraved. Despite the zebu bull being a domestic animal, it is generally not provided with an altar or trough, likely because the presence of the large dewlap precludes this. On the copper plate, it appears as though the engraver has run out of space to the right, and has had to indicate the tail by means of it looping at the top of the hindquarters.

Plate 7 depicts an Indian rhinoceros, an animal once found in the Indus River region, but now restricted to northeastern India. Again this is a comparatively uncommon image on steatite seals. On seals, the rhinoceros can face either right or left, and is depicted with or without a trough. On some rhinoceros seals, the feet are shown incorrectly and resemble those of ungulates. On the copper plate and some steatite seals, the detail shows good observation by the engraver; there are three toes on the rhinoceros foot and the only hair on the rhinoceros occurs on the ears and the tail.

Amongst the animal copper plates, Plate 8 is the most unusual as it depicts a sort of antelope that, with its forward projecting horns, is essentially fictitious or perhaps drawn from an uncertain description. Seals with similar animals have been found recently at Banawali, Haryana, India (Bryan Wells, pers. comm.), and one small steatite seal found at Chanhudaro in 1936 shows a virtually identical animal accompanied by an altar (Mackay, 1943). This unique seal also provides a pipal leaf similar to that mentioned for Plate 5.

Plate 9 depicts an Indian elephant, and similar images are found on several steatite seals. The elephant is almost always portrayed on seals facing left, and the presence of the trunk seems to preclude depicting an altar or trough on most seals.

The copper plates are not identifiable with any particular Indus site, based on style. It has been suggested that the plates should be associated with the Mohenjo-daro copper tablets, but profound differences set them apart. The best matching imagery originates from disparate sites, including Mohenjo-daro, Harappa and Chanhudaro, but there is no reason to attach any great meaning to this as other relevant seals likely remain undiscovered, and seals may have been distributed over substantial distances. A good example of geographical distance between clearly related objects is the famous bronze “Dancing Girl” found at Mohenjo-daro, and a sherd of pottery, found at Bhirrana, Haryana, India (about 600 km distant), showing a similar profile (Figure 11).

The nine copper plates are unusual amongst comparable copper tablets as both image and text occur on the one side of the plate. It has been argued that some copper tablets may have served as special amulets, and were carried, perhaps wrapped in cloth, on the person. However, the function of the plates here is clearly to impart an image as indicated by the reversed asymmetric Indus script characters. The same occurs with steatite seals, but here the engraving is deep and robust such the seal is capable of leaving a strong relief impression in a pliable medium such as moist clay. Trials with plasticine showed that the copper plates left at best a weak impression (Figure 12). The images imparted were generally indistinct, and relief lines in terracotta would have been quite fragile due to their fineness. The resultant sealing would have been far larger than anything known, and inherently prone to breakage.

The animal images on the copper plates are very similar to those from certain steatite seals, especially from Mohenjo-daro. The two copper plates with deity images resemble artifacts found recently at Harappa. It is possible that the copper plates served as a library or set of templates for the manufacture of steatite seals and related objects. The occurrence of lengthy text on the plates perhaps provided detail or instructions for craftsmen. The reversed script means that the plates were designed to leave an imprint: 1) either directly on clay, which seems unlikely, or 2) or on a different medium through the transfer of pigment, i.e. printing. As indicated earlier, these plates have a number of attributes that suggest they were meant for a special purpose. The copper plates are unusually thick, and this is surprising as it is recognised that metal was a precious and efficiently used commodity in the Indus Valley. One explanation of the robust nature of the copper plates is that these plates were designed to take substantial pressure, as required in printing. There is evidence that the plates have lost definition of the inscribed image and text; this could have occurred through a combination of surface corrosion, abrasion and repeated application of substantial pressure. Hedges (2006) has shown that with Renaissance copper printing plates, the chief cause of loss of detail is not so much the pressure of a press as commonly believed, which would tend to broaden the lines, but is erosion to the surface of the plate, both through atmospheric effects and repeated cleaning and polishing of the plate surface associated with inking. Over time, the usually V-shaped grooves created by a burin, which hold the ink will tend to become seemingly narrower and narrower, until they disappear. Hedges, in examining subsequent editions of images taken from many different copper plates, estimated that the loss in definition was about 1–2µm per year. Plate 9 (elephant) is instructive here, as the outline of the elephant’s back has completely disappeared toward the centre of the plate, whereas it is quite apparent toward the right. Assumedly cleaning and rubbing of the plate was more sustained toward the middle. As the climatic conditions and associated corrosion are unknown, the wear is not directly comparable to European plates, but nonetheless the decrease in line width from 400µm to 0µm indicates substantial length of usage. If the wear were due to producing sealings with terracotta, one would expect erosion within the incised lines and overall blurring of the image as occurs with well used steatite seals.

The proposal that this unique set of copper plates was designed for printing is indeed radical, but offers the most obvious reason for their existence. The principles of printing were perhaps known to Indus Valley artisans through the ancient technique of ajrakh, printing fabric with woodblock designs. It is possible that the copper plates were created firstly to maintain a permanent record of the standard designs on seals and tablets, and furthermore provide a cheap and portable means to distribute standard designs to craftsmen that carved seals in the Indus Valley region. To test this idea, an experimental trial printing was carried out with the plates by Marco Luccio, an artist and master printer based in Melbourne, Australia. Two printing inks were tested: 1) a water-based ink with ferric oxide as the pigment, and 2) an oil-based ink with carbon black. Prints were first trialled with rag paper, but then were printed on tussah silk cloth and parchment, materials which were likely available in the third millennium BC. Almost no organic materials, such as cloth, leather or wood have survived from Indus civilisation, although impressions of woven fabric have been found on terracotta vessels (Kenoyer, 1998; 159). Recently evidence of native silk fibres has been found at Indus Valley sites (Good, Kenoyer and Meadow, 2009), and tussah silk is a cloth still manufactured in northern India from the cocoons of the wild silk moth Antherea paphia, a species closely related to that identified as a silk source by Good, Kenoyer and Meadow. It is known that the Egyptians used leather in the third millennium BC for writing, and parchment documents survive from first millennium BC Babylonia (Diringer. 1982, pp. 172–174). Given the age and condition of the copper plates, the results on all three media tested were surprisingly good, and an example on tussah silk is given in Figure 13.

The implications of this are truly remarkable. It is possible that true printing was first discovered in the Indus Valley in the third millennium BC, at least 1500 years before any other printing process was recorded elsewhere, and the prints taken from these ancient copper plates provide the earliest known artwork in printed form. While this conclusion is astounding, all evidence points to the copper plates being genuine artifacts from antiquity, and their function as special.

The nine different copper plates appear to be the sole surviving members of a set of a unique type of copper plate not seen before among Indus Valley (Harappan) artifacts. They are quite different from the corpus of other metal plates or tablets recovered from Mohenjo-daro and Harappa, as they are larger and much thicker, but most significantly they bear inscription only on one surface and the script is reversed. Data from all tests, including x-ray fluorescence metal analyses, conventional and scanning electron microscopy, and metallographic analysis are totally consistent with metal artifacts from Indus Valley (Harappan) civilisation, c. 2600–2000 BC. Similarly, the iconography and script relate well to other Indus Valley artifacts, such as seals, made from steatite or terracotta. The precise source of the copper plates remains unknown, but is assumed to be either Mohenjo-daro or Harappa, based on iconographic similarities to known copper tablets and steatite or terracotta seals.

The copper plates are highly significant for two principal reasons. Firstly, they bear inscriptions in Indus script, a language that still remains essentially undeciphered, and one plate in particular bears the longest known single inscription in Indus characters. It is possible that, unlike the relatively common steatite seals where the few incised characters are generally deemed not to relate to any image on the seal, the text on the copper plates described here relates directly to the images, and may thus present a unique tool to progress the epigraphic analysis of Indus script.

Secondly, the fine and shallow engraving, the robust structure of the plates, the wear of the inscribed metal surface, and the reversed characters, are all consistent with the copper plates having a function for printing. Trials with simple ferric oxide and carbon black inks confirm that the plates can provide, even after over 4000 years, quite satisfactory printed impressions on media including silk, as would even been available four millennia ago. Thus it is suggested that these unique cooper plates are the world’s earliest known printing plates, and moreover, would have provided the world’s earliest printed works of art.