There were 18 screen used coins, all identical copies of a 1705 dated Portugeese gold coin.

Now here is the full story on the coins and pouch. 18 identical gold coins where used during the scene filming. At the end of the shoot it was found that the dialog did not work well and the scene was rewritten that night. However, the crews had started destroying the set to build the next one. The next morning they were in a jamb to put things back together as the table that was used had been smashed and some of the props missing. Another table was found and things quickly put together. This explains the discrepencies in the coins, bag, stack of currency and placement of props as the scene jumps back and forth between Indy and Lao.
The bag is actually turned inside out for a brief moment, some of the coins were missing so a couple of British pennies were painted gold and added expaining why for a moment the coins look diff. and if you watch closely you see the stack of bills go up and down in size.

This is all the background info. I was able to squeeze out of the former crew members I "interrogated". The one crew member was able to save ten of the coins of which I obtained a couple through the Prop Store of London. The bag came directly from another crew member that I met through my movie industry connections.
CR