I assume that all that is left of the original S250, following the upgrade, is the casework.
The display dial and rear panel now sport the MxV nomenclature and there is a new MxV user manual and test paperwork. Interestingly, the serial number has changed from the original 5115, to 5204!
CAF11229-9595-45EB-852A-631396F1682A by , on Flickr