Glad to help Jerry.
1897-1903 the Belgian makers even provided the load that should be used; another 12g
Manufacture Liegeoise proved with Mullerite (the Lion over M) for a service load of 2.70 grams = 41.67 grains = 3 Dr. Eq. (42 grains) "E.C." No. 1 or "Schultze" with 36 grams = 1 1/4 oz. shot
Please let us know if you find the gun in the catalog.
Unfortunately, the market for nice vintage 12g Belgian doubles, even by a well known maker, is not good today, so it is hard to estimate value.