Gasmask BS MT-4 with adapted Estonian mask ARS. Rare.

Gasmask BS MT-4 with adapted Estonian mask ARS, not common combination.   Most probably it's early war  modification due limited or bad supply. The mask has special adapter to use it with Russian tube and filter. There are factory markings on the mask: ARS-37 (Arsenal - 1937). It's pre-war made Estonian mask, could say modified copy of Britain mask. Used condition, but no damage. Unique example!