What Gary said.
Just be aware that those old selenium cells became inaccurate with age. Also, note the flip up part on the rear, from memory that stays down for an incident reading and is raised for a reflective reading. (Incident reading is when you point the meter AT the light source....reflective is when you point the meter at the subject....just like the one in your camera). Also, in reflective
mode, the meter always presumes you are pointing it at an average daylight scene, that is, something that is mid grey. On some
models you had to fit a white diffuser dome over the cell for reflective readings. (I think I got that the right way around).