This article from the Drum Guide might help.... or confuse further...??Link

It looks to me like the strainer and butt plate are in a reversed position. The strainer on early 60's Ludwigs should be right next to the badge and you have the butt plate there. around 1964-ish the strainer moved back a panel so that there was a space between the badge and the strainer.A P-87 is very likely what was on there as they were more common in the early 60's as they were pretty much common place as the strainer in the 50's. The 1950's WFL Buddy Rich model used a p-87 and was a very common drum much like the supraphonic was in the 60's. Wrap looks to be in good shape!

Any idea why the strainer and butt plate would be reversed like this? Does it mean anything in particular?

Maybe they were reversed at the same time as the snare beds had some work done on them. Way back in the original photo of the bottom it looked like they had been sanded a bit (where the white paint was removed). Perhaps after the beds were adjusted it seemed to play better (perhaps less sympathetic buzz) with the strainer and butt plate reversed.