Having some issues with this one, The Perforations I'm reading (double, triple checked with different gauges) but I ain't the greatest at using the gauge Is 11.25 x 12 So I thought #96a nope 1901-03 This stamp was cancelled in 95 So it would have to be a #86 11.5 perf? Can't make out the "watermark" impression (type 1 or 2?)
Perf 11-3/4 all around is correct for the issue mentioned and is what is used by the Swiss catalogs like Zumstein. Scott rounds the number probably because most gauges (still) don't have measurements to the nearest quarter.
For the Standing Helvetias, it is important to check the watermark and perf again after the first evaluation. It is also good practice to measure perfs on all four sides since the stamps do get reperfed and you could be using a measurement of a reperfed side.
Don't know how to show it, but best I get on the sides are between 11- 11.1/4 I just figured the paper shrunk :) Both left and right are the same. This is 11 not a perfect fit (not a 11 3/4) my gauge doesn't have dots for this measurement or 11 1/4