I'm getting ready for summer, when I love to take my little 1937 Voigtlander Bessa 6x9 out to the week end events etc. The camera has no meter, so I've been using my Minolta Flashmeter IVf to meter incident light. I also bought a Zeiss Diaphot from the 1920s, but it's hard to use in the field. Looks cool though. Anyway, I need a nice small meter for ambient light. I really wanted a Digisix but those are over $100 used, even (more like $150.) Then, I remembered I had a lust for a Zeiss Ikophot, a meter from the 1950s I think. They are so cool with their gold chain and creamy white dial! They are selenium cell though, and on eBay few sellers seem to want to claim the meter is accurate, only that it's in "working order." Hmmm. I am tempted to buy one that is claimed to be accurate. Has to be the sexiest meter ever made! I would like it to read up to ASA 400 as I mostly shoot HP5 and Portra, but I could work around that. How big are they? Would this be a good choice for me just wanting something cool to go with 1937 Bessa and meter ambient for b&w film? Or, what else is out there and really cool? (That works!)
Many ebay sellers will know that theirs is dead, as the vast majority are - the German (in mine AEG stamped) cells Zeiss Ikon employed seem to be particularly subject to weathering and oxidation. Some even have the cell missing entirely - after the demise of Zeiss Ikon, many repair people resorted to butchering meters to repair Zeiss Ikon cameras employing the same cell.
Try to get the seller to confirm that the needle is responding to light, and try to pick a later one (they were made until the late sixties or even early seventies, and later runs often seem to be a unassuming grey) - but it is a risky purchase at the best of times, even seemingly good meters will sometimes fail after a day of use.
The round cells used in the meters of Norwood and Weston lineage seem to be more long-lived and reliable - if you don't insist on a all-German kit you'd have less issues with one of those.
I used a Leicameter-MR for years with transparency and negative film (and as an enlarging meter, held sensor-up on the baseboard). The mercury cell isn't available anymore, but mine works fine with the usual replacements. The analogue scale is easy to read to 1/5 or 1/10 of a stop. The only issue is knowing where it's pointing.
Get the later black Ikophot that takes 9V batteries. As a bonus, the dial lights when exposure is correct, making it easier for my tired eyes to read. I can give you a couple of tricks for adjusting these if you ever find one.