A quick internet search seems to definitely point to 30's De Havilland passenger airplanes... DH.89 or related models, which all seem to have this seat but with armrests. Everything else matches : shape, cushions (back torn off in your example), leg design,...
A few options : either it's a 3rd party seat manufacturer that may have sold them to different aircraft makers, but I somehow doubt it, since most makers in the 30's made all of their parts (besides engines, tyres, etc.).
Or it's for a specific 30's De Havilland passenger model with an enclosed cabin, so not the 89, maybe not the 90... But I don't know enough about their history to identify all of them.
Or, probably most likely, they offered an option for seats without armrests, either to save weight/cost, or to make for a quicker emergency evacuation. So perhaps some military versions of the DH.89 had seats without armrests, those aimed at training rather than transport, for instance.
Two ways to find out more : a detailed history of 30's De Havilland airplanes or contacting the people who have been restoring the many flying exemplars around the world today and who are bound to know a lot about details like these.
If you find out more, let us know !