I beleive the O/U is a Model 203 E with a proof date of Feb 1972 & the SxS is a 447 SL with a proof date of Nov 1981. You will not find any model numbers that I am aware of on postwar Merkels.

The best way to get an idea of retail price is to look at the asking price for comperable guns for sale on web sites such as gunsinternational.