Non Op
Or non operation is what they are called in Cali. It was really stupid you had to pay every year to keep it on a non operational status. Somewhere in the mid to late 90's they changed it to a one time fee. If it wasn't non oped it could be dropped off the computer. For some silly reason they could not keep all the vins and plate numbers in their puny systems. It worked out for most as back fees including the yearly non op fee or the unpaid registration fees were wiped clean.
Some money grubbing politician figured that Cali. was loosing big bucks and they stopped letting about 4 year back registration vehicles get a pass on their back fees. People buy cars motorcycles and even trailers and can get a rude awakening when going to title the vehicle.
The reason I bring this up was their is no such record of non op or off computer record numbers here in Cali. or I would guess most of the colonies

We basically have a wait and see method of seeing what gets pulled out of a Barn or most likely a outlying area where cars are left to melt back into the earth.
The Brits do a way better job at it which also makes it harder to allow a car to slip below the radar and be re created. In the old days AAA or other non law enforcement types were allowed to verify vin numbers and re title cars. Not any more it is almost impossible to not have a trailer trip to C.H.P. inspections and verifications. Possibly why eBay has given us some Tigers lately with no vin or a badly home brewed one and other questionable but real Tigers.
Maybe I strayed away a little from your question but it is way more than checking registry, and sealed DMV records, "remember Rebecca Schaeffer," a hottie Hollywood actress that was DMV record stalked and killed. You used to be able to march in the DMV and get all sorts of info. not anymore!
The club and meetings get old members that show at events like Woodley Park that claim to have 5 or more cars, and stories abound like "oh the first one I bought cost me $350 dollars," but none of them run. Other serial hoarders are in the club as well but I have not seen those guys in any Sunbeam yet. Outside of a Tigers United the most I have seen at any event was at Woodley park if it doesn't rain its fab.
Time stands still for no man or machine, as we say in the boating world use em or loose em as father time rots em apart.