Help With ID Of 751A Single Versus 769A Reprint

Years ago I purchased the subject stamp single as a 751a. However, in remounting recently, I am questioning its original identity. It appears to be more likely a 769a single.

It is mint but without gum. Being a top center stamp of the pane, the top margin appears to be very slightly larger than that of my real 751 souvenir sheet, sample of one.

Does anyone know what the between pane margins were on the original 751 souvenir sheets? What variation in cut margins were normal as issued? Were any full uncut sheets ever issued that could possibly have sourced my single and been hand-cut and de-gummed?

If my single only had a much larger top margin firmly reflecting the 23mm gutter of the 769 reprints, there would be little to question.

Thanks for any suggestions or opinions!

Full sheets were available and are still around. Mint and used pairs are also fairly common.

751a = gummed
769a = ungummed

Thanks fellows. The lack of gum would be the obvious deciding factor if I had found the stamp in a shoebox. Only having acquired it from Mystic on approval years ago and they had identified it as a 751a leads me down the questioning trail (not that they are beyond making dumb mistakes, especially on low-value stamps).

Unlikely possibilities might be:
Someone cut up an original Farley Folly sheet (yikes).
Someone mounted/hinged and unmounted/ungummed it over the years.

But in either case, I suppose that would re-ID it as indistinguishable from a 769a single anyway. I haven't discovered any documented differences in paper or ink (other than gutter width) to distinguish the reprints.