mtdoc, Thanks - just to confirm I understand correctly - the earlier serial number units make it easier to replace the battery without losing data (ie, in this respect the earlier serial number units would be preferred) - yes?
Related question: if you lose the calibration data during a battery change will the unit 1) fail to operate or will it 2) operate but be grossly out of order or will it 3) be reasonably close on measurements (but not precise)?
Thanks again, EF