Finlands bank (Suomen pankki) seems to keep old coins. I was in the banks museum, and I saw many coins and banknotes worth thousands.
There was a post card with a picture of a pile of 20 markkaa coins (6.5 gram gold coin, from the 1870-1910's). I am pretty sure the bank has a lot of old coins, probably even some trial coins.
Banks and its museums may always keep old coins, probaly the ones of their own countries.
In Bangladesh, The Bank Jadughar (Museum) keeps coins from British India, Nawabs of Murshidabad and Kolkata (the coin which our catalogue does not have), Sultanate of Bengal, Indian Kingdoms, Ancient and of course Bangladesh from the beginning and neighbouring countries. I saw another gold coin they claim to have been found and probably from Iraq (maybe an Almohad?). There are silver commemoratives which don't circulate.
Ok. Finland actually has a museum, but its not that big as the first set of coins were issued in 1864. The national museum had a place called "money cabinet" or something but sadly that does not exist anymore. There were almost all the trial strikes, banknotes and coins.
In fact Bank of Finland has even bigger coin and banknote collection in their main building but it is not open for public. I have visited it once and it was quite impressive collection.
Many if not all national banks has also some of gold reserves in old gold coins. There are examples of price drops when one starts to sell their stocks. Those unc beauties just sit in the vaults for decades and then thousands of them will flood the markets and kill the possible premiums of some date or whole km#.
I know US banks use to keep old US gold coins for reserved. But in the 1930's the US government outlawed them. Making them turn over all of them. At face value. Then melted them, shipped to fort knots. About 150 years of US gold coins are gone to make the gold in Fort Knox. Hundreds of train car went there. Of just gold coins. I heard of one were there were 20 to 30 box cars of just gold coins. After that burn I don't think any US bank would keep any old coins.
