Battery for OM-1/1N
You would need a mercury 1.35V battery which are discontinued (mostly) worldwide. Next best is an MR-9 adapter which is a metal can with a schotkey diode built in. MR-9 uses a 1.55V silver oxide battery (386 type) which gets stepped down to 1.35V. If your meter is working, the MR-9 is the perfect drop in replacement. I casution against using the alkaline 625A / 625U batteries, which are the same size as the mercury battery but are 1.55V. they will cause a 2-3 stop error in the OM-1 / 1N.
Originally Posted by modafoto