OK this is one for the "Old Guys" that chased DX before the USSR imploded.  As history for the newer hams, if you worked a Russian station regardless of where it was in that enormous landmass, your card went through PO Box 88, Moscow, USSR.  Period.  Mattered not whether the ham was in Latvia or Estonia or Uzbekistan or Kazakhstan, or an of the other countries, it wen through PO Box 88, Moscow.  To make matters worse their callsigns were extremely tough to decipher.  For example call prefix "UK" denoted Ukraine except for UK6C, D, or K which was Azerbaijan or UK6F, O, Q, or V which was Georgia, or UK6G which was Armenia, or UK8H which was Turkmenistan,  or ...... You get the idea.  Now, to make matters worse, in many cases their cards did not indicate what actual "Country" they were in, they would only show an Oblast number which, as far as I can tell, similar to a grid reference used only in the USSR.  Google shows 48 Oblasts in Russia and I've got numbers that go up to something like 190 (from memory).

I don't show a confirmed contact for Turkmenistan, Tajikistan, Uzbekistan, or Georgia.  Some of the callsigns tend to match all of the exceptions but if they show a city it doesn't really match up.  This makes me think that the exceptions weren't used 100% of the time.  Or people moved around some (was that even possible in the old days of the USSR?) but didn't change their call.

I've got probably a couple of hundred cards from the USSR from the 70's up to the fall of the USSR and I'd really like to determine whether I have those countries confirmed or not.  I think most of them show either a city name or an Oblast number and I have been able to verify some of them based on that, but not all.  The 4 countries I mentioned above are still missing in my list of confirmations (or even worked countries for that matter).  Heck, for all I know Franz Josef Land is mixed in there somewhere.

Does anyone know of a good reference for determining the actual country based on the Oblast number or city name?  Google occasionally answers the question but going through all those cards on Google would be a challenge in itself.  I would appreciate any pointers since I've wondered about it for many years and would love to answer it once and for all.  If nobody here has a clue I think I'll send an email to the ARRL DXCC desk and see what they have to say.  Someone somewhere must have managed to figure it out but it's over my head.

Thanks in advance for any help.

I bet @Gyprat can help you.

Could be.  After I posted that I remembered someone responding to a post where I said something about licenses in the USSR in the 70's.  Whoever it was seemed to have some first-hand knowledge but I have no idea who it was now.

He's your guy 100%.

Despite the captions, I checked a few of my cards against the oblasts listed here and they match.  Maybe of help for you.  Somewhere I have a QSL that has all of the USSR callsign prefixes on it.

ETA, these may help in the meantime.  It looks like you can dig into the links and cites/oblasts are listed too.
TERRITORIES, PREFIXES AND SUFFIXES OF THE FORMER USSR.
Territories, Prefixes and Suffixes of the Former USSR Amateur Radio Callsigns

That definitely helps, thanks very much for posting it.  I do have all the old call signs, ARRL posted them in the countries list in their log books so I'm good there.  I'll go through my cards with your info this week and try and make some sense of what I have.