How to identify a shipboard rangefinder lens

How can a surviving lens from a ship's gunnery stores be identified?

Identify the rangefinder marks fitted to the ship's guns during the owner's service, then compare the lens with those instruments.

The ship and the owner's service dates narrow the possible gun installations. Records of the rangefinder marks fitted to those guns provide the next filter. The lens can then be compared with the documented instruments associated with each mounting. This method ties the object to a specific fire-control installation instead of relying on its dimensions alone.