A couple of provenance questions for the group. Ebay only archives listings for 3 months - is there a website that allows you to go further back? A corollary is can you see the original listing somewhere if you know the item number? NGC certifications. It's easy enough to verify that a coin has been certified based on the registration number; however, how do you get the date a coin was certified? This date acts as another signpost to the history of a coin but I haven't seen it available anywhere. Thanks!
Sometimes you can find old eBay listings on Coryssa. NGC certainly has the date stored somewhere but I've never seen any way to access it. Perhaps you could email them if you have a specific coin to ask about?
I have around 2 million records going back to the mid 2000's but have no way to search them. I tried to make a accessible online database but it was too time consuming and the server to house them was getting expensive.
You can generally date slabs based on the style of the slab and label, since you can look up the dates of that slab generation.
I have the impression that the same axiom applies to slabs of ancients as applies to the average cellar age of wine in a household cellar in the UK. The latter (median) is apparently 45 minutes, ie half of all bottles of wine are opened less than 45 minutes after purchase. My general observation on slabbed ancients is that much the same applies: firms such as Heritage buy mass volumes of raw ancients from Europe, slab them, sell them, and when I and othera buy them we crack open the slab faster than a bottle of cheap Plonque. Total time in slab is usually very small. Of course there's a small group of ancient collectors who collect slabbed coins and will eventually sell them. But they are a minority for now. I generally assume any slab ancient I handle was slabbed yesterday, and when I find data eg a prior auction, that generally supports my assumptions: prior sales tend always to be raw. There are exceptions but the 45 minutes cellar age rule seems to apply most of the time
Coryssa's ebay crawler only goes back to 2012 (and as far back as 2007 for Roman imperials). As for the slabs, I bet that you can deduce the approximate time by the serial number. Rasiel