unknown coins from Tibet, help for identification.

Hello experts

who is an expert for coin from Tibet. Who can tell me how it works with dates, value and other characters on these coins ?
I have 5 coins with a diameter from 27 till 29 mm and weights from 4.5 till 5.2 gr. mat. silber (?)
Are these differences in weight and diameter normal for that time?
1

2

3

4

5


Thanks a lot for the information and help
easthook

With only 6 pages, You will be The specialist

I just tried one. Number 3 is obverse 2a with reverse 2a I think. The reverse photo is upside down so that what looks like a "9" on the right should actually look like a "6" on the left.

The date is circa 1870─1875 according to p. 5 of the useful document linked by FrenchLover.