A31, A32 and C32. (1931-32)
K32 and M32 would have an additional set of holes for the hand shift gate, which I don't see. The A31, A32, and C32 had the hand change gate built into the knee grip, so extra hols not required. Just two each side for the knee grip.
Basically the same petrol tank was used on the 250 & 350cc models for 1934, but no plating and no tartan. Also the bottom was three pieces of sheet metal, and not one piece incorporating the floor and the tunnel (like yours).
And again the same petrol tank was used on the 250/350cc models in 1936 (and any sold in 1937?), but the catalog shows a separate hand change gate, like the K32/M32 models.
-Doug