This whole post to Nexxo, Moff Jerjerrod, Lucianer:
T-64 was a next-gen ,revolutionary designed tank to complain with T-62.
T-62 looks loke older T-54\55 that look like small series T-44 that has gun from T-34 and new hull (sorry for my eng)
T-64 looks like modern T-72 or T-80 without any upgrades.
T-64 was sucsessful in middles of 80's, it's modernized to T-64BV (Т-64БВ in russian lang): new 125mm tank gun similar to T-72, ERA, new FCS and some another improvements. But base\design of tank was made with constructional failures so it was highly expensive to fix them everytime it needs (more often than any another soviet tank)

Some of them were at East Germany Group, but real battle is has only in Moldova-Pridnestrovye Conflict.
Now are most modern of old soviet tanks that are still in service somewhere in former USSR:
T-55s are decomissioned in Russia, there are just some export variations, most popular is T-55AMV (Т-55АМВ

: FCS, ERA, and other, you know.. And like Israel former-tank APCs, there are BTR-T project and prototypes (БТР-Т in rus lang), means APC-tank-based. Unfortunately, canceled by our Defence Minisrty that wants to destroy Russian army from inside.
T-62 and T-62M (additional armor blocks and small improvements, no ERA). It's became decomissioned in Russia in last or this year. Export variant is T-62MV (Т-62МВ in rus lang) - ERA included +some new adds.
T-64 - Ukraine - modernized i to "Bulat" project. Russia: T-64A and T-64BV are in reserves and disassembling because it's factory now in Ukraine.
T-72 is: T-72B (Т-72Б in rus lang), T-72BA (Т-72БА - not massive, over 200 to 210 units), T-72B(M) (Т-72Б(М

- non-official name, just latest T-72B with new-age ERA and some adds after 1985 and before 1990). T-72BU (T-72B-upgraded, Т-72БУ-улучшенный

was renamed in 1992 to basic T-90, improoved to T-90S and T-90A (Т-90С, Т-90А

.
T-80s are: T-80U(K) and T-80BV (Т-80У(К

- К means commander(командирский

unit with additional communication adds) (T-80БВ - a little bit obsolete but still in service).
Our Defence Ministry brokes our "Object 195" (T-95) and "Object 640" (Black Eagle) so no more new Russian tanks in world before this traitorus gov-nt would be over**rown. Also, Su-47 "Berkut ", "Sprut"(Giant Squid) Airborne SPG, BMD-3 and -4, BMP-3, Koaliciya-SV (Коалиция-СВ, real upgrade of MSTA-S SPG to two barrels) and some more almost perfecr projects were canceled...