For the period from 1919 Jul 1 2:00 to 1922 Oct in the Europe/Moscow zone the Europe file says to apply the Russia rules with the format MSK/MSD:

                                                2:30:48 Russia   %s          1919 Jul  1 2:00

                                                3:00       Russia   MSK/MSD           1922 Oct

However, the Russia rules show three different offsets during 1921, 0, +1 and +2:

Rule       Russia   1919       only       -              Aug        16           0:00       0              -

Rule       Russia   1921       only       -              Feb        14           23:00     1:00        S

Rule       Russia   1921       only       -              Mar        20           23:00     2:00        M # Midsummer

Rule       Russia   1921       only       -              Sep        1             0:00       1:00        S

Rule       Russia   1921       only       -              Oct         1             0:00       0              -