I'm getting ready to make some Waterhouse stops for my Dallmeyer 3A. Even after searching here quite thoroughly, and Google efforts as well, I don't find the information about the actual focal length and wide open f stop. (Probably my search techniques, but frustrating none the less.)

Can anyone here please help with that data so I can calculate the needed stopo sizes for the Waterhouse stops?

Many thanks in advance.

Tim