Derby production codes

While the later units of the Foth Derby cameras can be uniquely identified by the serial number of their lenses, the early units do not carry any serial numbers. Careful inspection will reveal the presence of manufacturing codes, most likely representing the staff codes of the individuals who machined and assembled the lenses and camera bodies

The manufacturing codes usually occur on two locations of the lens and they are generally the same.

1) There is a recess in the lens thread that holds a flat tension spring. A number can be stamped , or more commonly, scratched in underneath the spring. To make that accessible, you need to unscrew the focus stop pin and gradually unscrew the lens until the recess is exposed. There is no need to unscrew the lens in total ...but if you do, remember which way it came off as you need to thread it back the same way for the focussing scale to be accurate. You easily can pop off the spring (it is loose, usually only held in place by a blob of dried up grease. When putting it back in, insert it into the recess, and press it down with your thumb as you screw down the lens.

lens partially unscrewed to reveal recess and tension spring

number stamped into the recess for the tension spring

number scratched into the recess for the tension spring

2) The second location where the number can be found is on the side of the lens barrel. For this you need to unscrew the whole lens mount off the lens board (the remaining two screws) and pop out the lens assembly.

number scratched onto the side of the lens mount