Belgian A.G.20
The Belgian A.G.20 facepiece was identical to the A.G.15, including the embossed "A.G.15" stamp. But instead of having a small filter attached directly to the mask, there was a corrugated hose leading to a much larger filter. Most likely intended for civil defense, this example was made by L'Anti-Gaz in 1939.
L'Anti-Gaz = "Anti-Gas"
Similar masks in my collection: Belgian AG15, Belgian M1931, Belgian M1934, Belgian AG9, Italian S.A.B. M33, Italian I.A.C. M33, Spanish M33
Manufacturer and model stamp on cheek 'L'ANTI-GAZ S.A AGREE PAR LE GOUVERNEMENT AUTORISATION No121" "II"
Stamps inside mask "37" "33"
Stamp inside mask "25"
Manufacturer stamp on hose "L'ANTIGAZ"
Stamp on hose "1939"
Filter stamp top view "BREVETE F-39-A"
Filter inspection stamp side view "Controle D"