I read the theory about the origin of the rangefinder here Official rangefinder talk, and as I know this was not confirmed 100%. I searched the internet about headshells, cartridges and tonearms for turntables or phonographs to find some parts that match the rangefinder. I searched several sites and found these parts:
Thorens TD 150 II headshell:
The shape is similar to the rangefinder's shell. And this one is similar in other ways:
Thorens TD-145C headshell:
The AEU GP40 520 cartridge with needle has the basic shape of the rangefinder inner part:
And the rangefinder stalk is similar to these tonearms:
Pickering Fluxvalve Unipoise tonearm
Shure M16 tonearm
All of these parts are made before 1977 (I don't know the year of the AEU GP40 520 cartridge).
It is possible that Brian Archer (we know this thanks to Art who posted here Fett build history and found parts suppliers) who did the rangefinder really used full parts from phonographs or turntables or just made the rangefinder using those parts as reference. Maybe there is somebody who will find (or not) the original parts used (full or reference).