I have a solution in Tortoise SVN, with around 100s of copies of a solution, now I am not sure which copy dll is deployed in gac, I can see date modified or something in Gac, but its not matching any of copy in SVN (I exported all near to date dlls). is there anyway I can compare both dlls.
You can mount the GAC folder to a drive letter in explorer and directly access the real DLL files by running the following command:
subst z: c:\windows\assembly
Then browse to the 'Z' drive in explorer, and go through the namespaces to see which physical DLL is registered with Windows.
At that point you could copy out the DLL and compare by exact file size to your candidates from SVN, or calculate some kind of hash (e.g. MD5) to determine which version matches the one that's registered.
P.S. Don't forget to unmount the drive once you're done.