Just did some checking on this one and it appears genuine and it's currently at a good price. As for the 123 reference number, Breitling doumentation seems to add a 7 sometimes so I'm 99% certain it's documented as a 7123. The serial number correctly dates it to 1946. Unmarked movement wouldn't be a deal breaker for me since it's really a low end model and old enough to probably be correct.
http://www.ebay.com/itm/121045437997?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
