I use the Heidelberg archives quite a lot. The trick - if I remember correctly - is to enter a name such as
Cahn or one of the other
auction houses, then there is usually a line with something like Catalogs -
Auction Catalogs -
Cahn... or similar. If you click on the "
Auction Catalogs"
part of the line then you often get a list of thousands of
Auction Catalogs. But it does not sort them into ancient, modern, middle ages etc. of course, because many catalogs contain a mixture of coins from all ages.