This is a Polaroid Pack Film Holder Model 405 that comes in the original box with the dark slide and instructions. The Polaroid 405 back allows the large format 4x5 photographer to utilize Polaroid (Fuji FP-100C) 3x4 pack film for proofing. If you are looking for a deal on a 405 back for your large format kit, this is it! For use with Polaroid 3 1/4" x 4 1/4" instant pack film.
This back is in good cosmetic condition - with some wear marks on the casing from normal use - and seems to be working well. Rollers look good.