The original Derby took 36 x 24 mm exposures and had an open type, folding, finder. The second model (c.1931) took 4 x 3 cm exposures and had an enclosed finder. Around 1934 delayed action was added and the fastest lens available was f2.5 rather than f3.5. Around 1937 existing models were designated Model 1 and a new version - Model 2 - was introduced having interchangeable lenses. Around 1939 a rangefinder version was introduced by Foth in Paris.

One of the many 16 on VP size roll-film cameras produced around this time, the Derby is unusual in having a focal-plane shutter. It was a very popular camera which sold for about ⅓ (£5.8.6) of the equivalent Leica. A rangefinder could be fitted to older cameras by the distributors in the US.