Got me replacement bulb for UV light and was able to get a pic of the 25c Honey Bee tagging.
The top stamp pair shows what I assume is 'Small block" tag
The bottom PNC3 shows what I assume is "large block" tag
The PNC3 is plate # 1. The edges of the tagging are sharp so I do not think worn mats come into play here. As can be seen, the "small block" is not only narrower, but is also shorter a bit. Notice something else... The corners of the tagging. I seem to remember something about these stamps being called round corners and square corners. Since the corners of the stamps themselves are the same, maybe it is the corners of the tagging being addressed with "round" and "square"?