A good idea, but beware that that doesn't necessarily give the correct view of what a real cvs checkout gave at that time, since the ,v files have been moved around etc.
The early days were certainly a wild west in this regard (also, there were module imports from other repos as well, which further complicates comaparison). For 7.1 and up, I _think_ it should be more or less ok as long as you dont try to e.g. check out a 7.2 from the 7.4 repository etc.
I have a list of all the irregularities which the svn converter compensates for, but I guess it will be a better check if you don't depend on that one being correct...