The Tibetan manuscripts from the Dunhuang cave and other Central Asian sites contain a variety of different kinds of seal. The seals were stamped on official or legal documents, some of which were produced locally in Dunhuang, while others arrived from further afield in the Tibetan empire. The most impressive seals are those that were stamped on the documents of the offical responsible for the Central Asia regions of the Tibetan empire, known as Dekham (bde khams). The example here, from Pelliot tibetain 1111, is from the accounts office of the Tibetan official in charge of this region, the Delon (bde blon).This seal shows two figures, one on a high seat probably representing the Delon, and another who is in a suppliant position. Perhaps it represents the payment of duties. Individuals carried seals as well, and these were used to stamp their own documents, which involved sales, loans or hiring agreements. These individual seals, known as sug rgya, are less impressive than the official ones, and are always round rather than square.This seal is on a letter found in the Tibetan fort of Mazar Tagh (Or.15000/204). The fragmentary text mentions measures of flour, so it was probably an order or a demand for payment. Finally, for those without the means to have their own personal seal, it was possible to sign documents using a "finger seal" (mdzub tshad). This involved drawing a box around the finger, sometimes adding lines for the joints, and writing the person's name inside the box.This document (Pelliot tibétain 1101) records a loan by a Tibetan official to local Chinese people. Three of these have added their finger seals to the document. All of these types of early Tibetan seals are quite different from Chinese and Khotanese seals, and there is more work to be done on how they were used, and by whom.References:
Stein, R.A. 2010. Rolf Stein's Tibetica Antiqua. Trans. A.P. McKeown. Leiden: Brill. 97-115. Takeuchi, Tsuguhito. 1995. Old Tibetan Contracts From Central Asia. Tokyo: Daizo Shuppan.