You guys might have picked up on something.
I don't specialize in varieties so I cannot give you a positive answer. There were coins struck in Leningrad but at the same time, some were struck in the UK.
Some trial coins were tested in the UK, which then were brought over to Russia. I did remember reading this somewhere.
Just in case you didn't notice, all of the coins remained to be the same size from the Tsar era.
1925 - got rid of the massive silver ruble.
1926 - coins were slowly reduced to be in smaller size form, starting from the bigger copper coins.
1928 - last of the 1/2 kopek coin to be struck
1930/1 - silver no longer exist in circulation
Figleaf - would be nice to see your coins.
