If I remember correctly, it's not really a prototype of the P90, but rather a "workshop model" or something like that (I don't remember the gunsmith terminology). It's not meant to resemble the final product in any way, or even be a usable weapon. Its sole purpose is to test that the internal mechanisms work. Basically, it's the firearm equivalent of the Northrop Tacit Blue.

Either that, or it's the army variant of the Bosch vacuum we had in the kitchen when I was a kid.

i truly do not understand just exactly what the hap is fuckening here

!forgottenweapons@lemmy.world

The FN P90 (matching the text in the pic):

Not only did the FN P90 fire a revolutionary and original ammunition, but it also marked the advent of two significant technological events in the history of gun making at FN. First of all, its patent specified the placement of the 50-round magazine along the barrel and axis of the weapon, while all the machine pistols of the time were still encumbered, either laterally or vertically, by their long magazines. Furthermore, through the power of its spring, the FN P90 magazine itself ensured the rotation and exit of the ammunition into the gun's chamber. Also, for the first time in FN's history, the development team chose to put their faith in the possibilities offered by technical polymers. This choice placed FN Herstal definitively at the forefront of high tech technologies. More than 50 percent of the new arms later developed by FN Herstal would be made of composite materials.

(One) Source

That thing on the bottom looks like it came from the set of a 1980s sci-fi B-movie.

I imagine the climb on either of those would be significantly reduced.

I kinda want that naked p90 on the top