I have many working copies of same repository on my PC, they are in different folders.
I was just looking at the SVN log of a file I checked in some time ago and I can't remember from which working copy on my PC I did such check in.
Is it possible looking at the SVN repo log to see from which working copy a certain file revision was checked in? I don't know if the log stores somewhere such information.
FMY: is it possible in GIT/Mercurial ?
Not possible in SVN. In Git/Mercurial there's no such thing as a check-in. The closest equivalent would be committing locally and pushing to a remote repository. In which case, you also can't see specifically where that commit came from (although you can of course see the associated user.)
For both SVN and Git/Mercurial, you could change the user for each working copy and use that for identification purposes although it's unclear to me why that would be necessary.