The fraction stamps '7/8' and '3/4' were done with individual stamps for each number and the cross bars themselves.
Not a single stamp for each fraction with the entire figure on it.
Just my observation,,not really knowing what way they may have been doing them in the proof house(s)..(individual number stamps, or fraction stamps).
I would guess they have fractional stamps at hand from the ones I've looked at being nice and even and straight.
The '3/4' is really off center and crooked.
The 3 proof marks in question are the three stamped deeper than the rest of the markings on the flat.
Deeper, bolder and out of character with the rest of the finer, lighter stamped figures.
The proof stamp is multiple struck either from being bounced,,or perhaps trying to reallign after a poor hit.
A large faced single stamp struck heavily to get a good imprint will always bounce and give a double or triple imprint especially on a barrel/tube unless some sort of device is used to absorb the vibration of the strike. A lead form is often used.
Trying to reallaign a complicated figure after a light hit and restrike it almost always results in a poor mark.
I'd look very closely at the proof mark itself under a loop too. It doesn't quite look as detailed and smoothly produced as I expect.
But stamps do wear out and get replaced and/or recut over time so perhaps it's just not one of their better ones to my eye.
Just my observations of some variations in the markings themselves.
