Cyclo Benelux British 3 Speed 1/8" Rear Derailleur

Cyclo Benelux British 3 Speed 1/8" Rear Derailleur. It is stamped 4 sp 3/32 - 3 sp 1/8 near the lower pulley. I don't know much about these because they are before my time. I took many pictures, the only rusty spots are near the stamping and on the spring. The photos look worse than it is.

Vintage - 1950s - 1960s?

Condition - A few rust spots, see the photos.