So I happened upon a nice looking srt-201 and couldn't pass up the $30 price tag. Seems to be in good working condition everything works and the light meter even agrees well with several others that I trust. I have some questions for those who've more experience with this model.... 1) With regard to the light meter on/off/bc switch, do you just leave it on all the time or turn it on, make a few general readings and then turn it off? I'm used to the light meter being a lot easier to turn on/off (as on the late model pentax and nikon models for example). 2) this one came with the proper mercury battery installed(!). How long can I expect this to last? More importantly, does anybody know if this meter circuit will read correctly with a silver-oxide replacement? or, will that require the meter to be re-calibrated?