These ingots came in different shapes; the most common kind resembled horseshoes or donkey shoes, and were named "rta rmig ma" in Tibetan.
For small transactions, various consumer goods (which had about the same standard value among the majority of the Tibetans) could be used.
You can see this coin minted in 1918 (1552) in the tab of Images of coins, picture 18, and a preview of year 1921 (1555) here:
The use of historical money in Tibet started in ancient times, when Tibet had no coined currency of its own.
This is one of the most desirable coins of the Tibetan series, year 55 (i.e.
1921 AD) is the rarest (estimated price is US $10,000$15,000).
For the 17th century, the export of falcons to India is also recorded.