There's always a story to tell Peter. A lot of these coins as well as the survival rates of them depended on the Soviet economy back then, global financial status and politics.
The 1957 and 1961 coin sets were only sent abroad to foreign banks to educate overseas banks of their old and new coinage. Limited mintsets were made for 'special' people and were mostly sent overseas. Exception of this is the 1967 commemorative mintset as few tens of thousands were made. What I have traced is that a fair amount of 'scarce' mintsets were coming from Germany and from the UK, and a few from the US. Surprisingly some of the rarest mintset, the 1970 mintsets were from the UK. I traced at least 20 sets from there while I was actively doing my survey. Another tough mintset, the 1973 mintset - significant amount of them are from the US. Other tougher years are coming from Germany and US. As of why, I do not know but it might shed a bit of light of how marketing was done back then.
Production ramped up at around 1974-5 as the Soviets were awarded for the Moscow Olympics. Of course, it would be smart marketing to sell them to the West as there's no way a typical Soviet could afford coins. Possibly a common folk could afford only one of the Soviet silver olympic coins but that was around 50USD - hefty sum of money back then and that was about two months of savings. Gold and platinum would be out of the question and if one did attempt to buy them, some secret agents would have pulled you over and inspected your bank account and determine how you managed to obtain such money. Besides, while silver and ni-cupro coins were somewhat available to the public, gold and platinum didn't or you had to know the right people to buy them from.
Hence, mint officiers in Leningrad Mint thought it would be a fantastic idea to sell as much coins out to the West through the Mezhnumizmatika venture over in Germany.
Coins / bullions that were up for production are:
- Chervonets
- Common mint sets but in various packagings
- Medals
- Coins in ni-cupro, silver, gold and platinum
As Leningrad mint could not handle all of the production at once, some production were sent over to Moscow Mint to handle the increased demand. It should have worked out very well except it turned out to be a diaster which required a few years to recover.
As hinted in the beginning, three major factors caused the coinage program to become a diaster:
- poor Soviet economy, hence most of the coinages had to be exported to make a profit
- global finance seems to be similar to today - metal prices shot up to make the program very expensive and unprofitable. (remember the Hunt brothers?) Gold actually was MORE expensive than today if you include inflation
- the 1979 Soviet invasion of the Afganistan caused massive global boycott which unfortunately included coins and such
All these factors caused the coinage program to become a major diaster. Too many coins were minted and had to be remelted as precious metal prices shot up too high. After 1980, special coins in mint set pretty much halted with a big brake for fear of similar nightmare. This is why it is common to see mint sets from 1974-1980 (except 1976 as the 1976 20 kopek is a key date) and the next common mint set is issued from 1987-1991. The missing year gap of 1981-1986 mint sets are actually getting quite hard to find.
It was only in 1988 where the Soviet mints attempted to restart making better decision with their precious metal coinage which turned out to be a lot more successful which only breaked again in 1991-2 and 1995-7.
Hope that shed a bit more light from what I have researched. That took a while to investigate but quite worthwhile.