And it ultimately isn't any different from the copy I received a few years back to create this merge with. In fact, I recall doing the exact same speed correction.
If you got your tapes from the taper (assuming this person is telling the truth), then chances are yours are first gen dubs. Very few tapers part with their masters.
So thanks for contributing ! It's always appreciated - and we can at least be pretty sure it's a confirmed first gen copy now.
The Real Wizard