Need Help Differentiating Between Bureau Precancel "Styles" Pss-81 And Pss-86

I guess I'm having trouble with "fonts" - can someone tell me the easiest way(s) to differentiate between Bureau precancel "styles" PSS-81 and PSS-86 ? Thanks.

Have you tried www.precancels.com ? If you really go into precancels you ought to become a member


Peter

Putting the illustrations from the style chart side by side reveals an obvious difference in letter height.

Inconsistently, the Town and Type catalog mentions the text height for type 81, but not the distance between the lines of text; while type 86 is exactly the opposite by listing the distance between the lines of text but not the text height. The catalog could certainly be more helpful in this regard. Nor do they define or describe what "Linofilm caps" are for type 86.

That said, did you have a specific town with both types 81 and 86 which you could show or cite? I always start with the town listings and then refer to the style description if I need to.

Thanks, John - yes, Philadelphia PA on Scott #1614 - it's the only city that has both Bureau precancels on the same stamp. I have the 2020 Bureau catalog and the PSS style chart - I don't know why I didn't think to use images from the style chart side by side as you did.

It's hard to tell the chicken from the egg in your question.
As you can see from your excellent Philadelphia PA scan, the letters are almost touching each other in 86, and I always check the vertical positioning of the first letter in the state (or last letter) with letters in the city above to see if they're different (the P in PA is positioned different).
In short, I like to think of style '86' as in the '86-87' family of fonts, they have no other members. '81' is like the 70s styles, just they do not have periods after 2-letter state abbreviations.
Something tells me you are not looking at the "Style Descriptions (PSS #)" page in introductory pages of a PSS Bureau catalog?