As you probably know, the circuitry on many OM 4's was updated. I think the way to check for new circuitry is to do a battery check. If it turns off after 30 seconds, it's the new circuit. Even with new circuitry, there is still a drain so it would be best to remove the batteries if you are not using the camera. Could I put a word in for the OM2000? 1/125 flash synchronisation speed, 3200 ASA setting, 1/2000 max shutter speed, spot metering. Totally manual (except for the meter) so battery life is extremely long. Also, when using the self timer, the mirror and aperture pre-fire, so if you are using a tripod, vibration is kept to an absolute minimum. This can be essential if yoiu want to get the best from your lenses (it shares this feature with the OM 4 and OM 4Ti). There were lots of variants of the this camera made for many marques over the years (it's made by Cosina). The only one still in production is the Nikon FM 10, I think.