Overview of Mask: Edit
The Swedish Type 4 Gas mask is a WW2-era mask. It was made out of rubber, with canvas fabric on the outside. The interior of the mask had leather surrounding the entire outline (where the user of the mask's face would go) with a chin strap or chin "holder" to hold the chin in the correct position. The lenses had at least two layers, glass on the outside, with plastic film on the inside. Each lense is about 8.5mm with 6.5mm glass. The inner lense consists of the lense itself and a flexible metal suportive circular piece to hold the lense, which firmly sits on the inside of the main lense. It is able to be removed but the lense is very fragile, and can crack, being easily damaged with minor force or bending. A standard NATO 40mm filter should fit. The mask features a more uncommon exhale valve that can be screwed off, the exhale valve has a diameter of roughly 20mm. The straps on the back are two different strap sections. The one on the top is an upsidedown "T" intersection with 3 points of restraint on either side and one on top.The other strap has the ability to be hooked on with a loop on the lower part of the mask. Both straps sections use the familar elastic cords with a cloth cover that were used on other masks like the GM 38.
Unfortunately, it's unknown what filter belongs with this mask, but filters commonly sold with the mask typically feature markings of BICAPA, so it is likely that the BICAPA filters were the orginal or similar filter. It is a sterotypical small grey filter with a 40mm thread with wax paper covering the intake. When shaken, there is a light rattling, presumably charcoal.
Some masks have been sold with an extra green plastic type adapter for the 40mm thread but are very particular when accepting different filters.
On the top of the mask there is a leather strap that sticks out that is sewn into the strap.
There are inner flaps that often cover the date stamp/markings.
There are two different coloured masks, (rubber and canvas) the most common light grey version and a darker grey version.
Sizing follows the order of 1=large 2=medium 3=small