I am researching a recent acquisition with unusual dies, and I referenced ACSearch for example images. I found a handful of examples with the same dies. ACSearch is a pretty good resource for auction records after 1999, so I decided to subscribe to their premium service for 1 week (15 GBP). This seemed reasonable to me so I subscribed, hoping to find more die links in earlier auctions. I found that the pre-1999 entries for my search criteria ("didrachm ROMANO"), were limited to a few (23) entries between 1902-1934. Nothing between 1934 and 1999. A more generic search for "Sestertius Hadrian" yielded similar results with 54 examples, all in the 1920's-30's. The service may be quite useful to those who need quick access to hammer prices, but for my needs, I'm a little disappointed in their pre-1999 content. It makes a lot of sense that it would be more limited for the pre-internet era, but I would think that the more recent pre 1999 sales would be more useful with more current information and classification.
ACSearch only includes pre-1999 auction records from pre-WWII auction catalogues (exclusively German) which have been digitized by the Heidelberg University. One useful tip: when you look for a record in those catalogues (like your didrachm ROMANO) only the first coin of that type in a particular auction is usually found as the following ones of the same type are just inscribed with "idem" so you have to click on the "next lot/coin" to find more of those.
One thing that struck me when I paid for the premium service (mostly for hammer prices) was how many coins failed to sell at auction.
