Here's the finished auction listing for that visor and shoulder armor set.
A set of various armor castings from Richard Marquands 1983 sci-fi classic, Star Wars - Ep VI - Return of the Jedi. Made for the production of the film, the set consists of six pieces of various sizes made of vacuform plastic. The crescent-shaped pieces were crafted as rebel biker helmet bills...
propstore.com
I don't think that these visors were ever used in the final Rebel Endor Trooper helmets, as the other auction shows the visor as molded integrally to the armor ring, and these visors don't have the right shape to my eye.
A production-made Endor rebel trooper helmet from Richard Marquand's Star Wars: Return of the Jedi.
usm.propstoreauction.com
The screen-used visors are shaped more like a formal military dress cap visor, which has a shallower crescent shape, whereas these separate visor castings are shaped more like a squared baseball cap duckbill.
Peaked Cap Pattern by Kamui Cosplay
Dill Pickle Cycling cap sewing pattern (This pattern would work well for a Hoth Hangar Tech)
Another completed auction of interest is a backup buck mold that they created in production by filling the vacuformed helmet pieces with plaster.
Endor Rebel Trooper backup helmet bucks from the production of Richard Marquand's Star Wars: Return of the Jedi. Rebel Troopers wore their modified camouflage costume as they travelled to the forest moon of Endor.
ukm.propstoreauction.com
It's split right down the center "between the eyes" like the screen used pieces and has some excess along the seams, so it appears to be somewhat of a quick-and-dirty backup. Of note is that the visor as NOT a part of this backup buck. I still however think that the screen used helmets had visors that were part of the helmet armor mold because the fully-completed unused auction listing has a seam down the center of the visor. If the visor was cast as one piece as in the "various castings set" then that seam would not be there.