Thank you for submitting your item. This appears to be flatware of the very late 1960 to early 1970s. According to your description sterling silver, but I spotted a "90" on one of the knives, which would indicate that the set is silvplated with 90 grams of silver ( 90 grams of fine silver are applied to a surface of 24 square decimeters). Similar designs, but not as extravagant, were made by Robbe & Berking an a few smaller manufacturers in the Solingen area. I have never come accross this particular pattern in the last 30 years, and that it was produced by Carl Mertens is very surprising. The company is best known for the "mono" pattern and other very straight elegant designs. Apparently this flatware chest with this particular pattern is very rare but not very much in demand at the same time. Someone who has the same pattern at home and wants replacements might be willing to pay more than the high estimate.