We're talking about the screw mount Pentaxes, a subject that I am quite versed on. The Spotmatic was the first Pentax with meter. To achieve this, they cut off that end of fthe viewfinder frame. Except for the small area where the needle opening shows, is cut off in the finder, yet appears on the negative. This is the left-right 36mm dimension. As or the up-down 24mm dimension, either the bottom or the top is also cut off in the finder, (can't remember which) but appears in the negative. This means that the viewfinder is off-center in both directions, for a total of 85% actual negative. I recall it being noted in a 1974 Modern Photography review of he Spotmatic F. This same situation exhibits in the ES and ESII models. In fact it dates back to 1964 when the original Spotmatic was introduced. And it is entirely unacceptable. Referring to the same tests, Modern Photography also published their lens testing chart on the 50mm 1.4 lens. It was found to be a very poor performer. The 1.8's and 2's were much better, as are many of the Super Multi coated Takumars. but we are discussing on this thread the H1a and H3v series which had no meter. Therefor, the viewfinder right side does not have this cut-off problem. But they DO have the up-down off-center problem.
In about 2004 I shot the storm photo of a lifetime on a Spotmatic IIa, and that damn Pentax RUINED my framing because of the off-center problem. I was already struggling with it's stupid mirror jam upwards problem. Never again. I use a Nikon FTN because it gives 100% exactly as I frame it and the camera is as dependable as an anvil.