Getting right into the deep end are ya? Haha.
Okay so the whole A.87 thing got a little muddy over the years. Originally this form factor was made by an otd.kr member but it went through a few community revisions afterwards. First off, here’s a size comparison:
The main differences are the size (the PCBs got smaller over the years) and the stabilizer orientation. In most cases neither will matter, but for completeness sake, the original orientation is:
left shift: wire under key
spacebar: wire south of the key
right shift: wire south of the key
enter: wire north of the key
backspace: wire south of the key
After a while people realized that Cherry stabilizers wobble and rattle more if the wire is south of the key, in specific rows, though. So people started rotating them.
Then there’s the whole B.87 mess. The B.87 PCB was made by winkeyless and is smaller, has a few rotated stabilizers and has the USB port on the left side. Then some wonderful people got the idea to use that general design, but put the USB port at the A.87 position while not renaming their creation.
So, bottom line: look for the even 0.25u spacing, with the USB port right next to F12 and at the top side of the board. Anything else should just fit unless the plate was made to be an ultra tight fit around the stabilizers which isn’t that common anymore.