Some Tibetan Seals Illustrated and Described, by Derrick Dawson, issued in 1997.
The Seals of Tibet are part of the Postal Hisotry <of Tibet and very much colelcted and in demand. Tnhis book covers a total number of 67 different  seals as follows:

• Dalai Lamas (x7)
• Dalai Lamas Administrations (x9)
• Prime Ministers (x3)
• Regents (x3)
• Panchen Lama & Court (x8)
• Sakya Lama (x3),
• plus the seals of Monastic, Administrative, Postal, Banknote, Nobility, and Miscellaneous seals.

The book contans 97 illustrations out of which 42 in are in red/color.
A very useful appendix of Horyig and Tibetan characters found on important seals and their Roman equivalents finalizes this fascinating book.