BS-T5 ( BN T5 prototype)gas mask, canister with valve system especially for this type gasmask- T5. The mask T5 has two different types, early one with glasses fastened inside of mask and non repairable/removable. IMHO, this type of eye glasses system is typical for pre 1933 year masks
The filter shows that the gasmask made in August, 1929 year. Filter has it's own number (bottom). And name of the system at the top - BS , ink stamps on the mask is visible but unclear. Very nice and rare gasmask itself.
And original picture being worn T-5 mask