Tamkas

At first: it is not "Tangkas" (this is the Tibetan painted scrolls) or any other version with the letter h integrated like "Thangka" or "Tangkha", but Tamka.

Tamkas are the first Tibetan coins in 1791 and they were minted until 1953 (that was from the very beginning to the very end!). The Tamka derived from the Nepali Tamka or Mohar (and therefore had it's root in the Indian Tamka). A Tamka ideally should have xxx g.

The Tamka was taken over from Nepal. The weight originally was 10,5 g silver. Around 1640 the Malla Dynastie in Nepal refomed the weight to 5,4−5,6 g. The coins of this weight were called mohar, or Tibetan bal tam.
This bal tam (transl.: Nepali Tamka) was the base/ foundation/ origin of Tibetan coinage. The first dated Tibetan coins from 1791 were such Tamkas with the weight of xxx g. Before in Tibet Nepali Mohars circulated from xxx to xxx (see Nepali coingae for Tibet). The Nepali Mohars were hacked into fractions of the Mohar thus becoming the base for the Tibetan coinage system. The Mohar/ Tamka coins had 8 petals along which the coins were chopped. Even after the coinage system became decimal after 1909 the denominations of the fractions of the Tamka pertained: 5 Kar (3 petals), 7,5 Kar (4 petals) and 1 Sho (5 petals).

The Tamka is THE coin of Tibet and THE denomination that Tibetans counted in. Even the decimal coins of Kar, Sho and Sang issued after 1909, were issued in the fractions of the Tamka, making 7,5 Kar coins (1/2 Tamka) and 1,5 Sang (10 Tamka), 3 Sho (2 Tamka), 3 Sang (20 Tamka) etc.

The Tibetan Tamka never has a denomination written (showing that EVERYONE anyway knew what it is) and in the case of the later Ganden Tamkas is never dated. It always has the 8 lotos petals carrying the 8 Buddhist luck symbols and a lotos flower in the center, resembling the Nepali Mohars.

There is an enormous variety of Tamkas, the best attempt to categorize them was done by Nicholas Rhodes in his article in the ONS (Oriental Numismatic Society), see here.

While I attempt to give examples of ALL Tamkas here, I ommit here Tamkas of the sino Tibetan coin issues, which are rare and only were minted in ther year Qinalong 58.