Originally Posted by Rob-F
If the M6 is an M4-P with a meter, it is also an M4-P with shrunken framelines and a condenser lens missing from the rangefinder. ...
Sorry, but the same condenser is missing from the M4-P (removed during the M4-2 run). The framelines in the M6 were originally adjusted based on distance and to accommodate the meter diodes.
The very last group of M4-P cameras had the same zinc topcover material - and with the flat windows to boot! The zinc material was cheaper to produce than brass.
But please keep in mind, I said The M6 is essentially
an M4-P with a meter.