Camera Body: Remove the film back from your camera. The serial number is engraved on the inner face of the camera body, typically starting with 2 or 3 letters followed by numbers (e.g., RC123456 or 10EU45678).
Model Name: Look at the top plate or front of the camera for the engraved model designation (e.g., "500 C/M", "503 CW", "SWC").
Tip: For most accurate results, select your model from the dropdown. If you're not sure of the model, just enter the serial number to see all possible matches.