The Crydom SSR I ordered on Ebay arrived today.
https://www.ebay.com/itm/273522773981It's exactly what is shown in the listing pictures, including the Crydom box and the 2006 date code. It comes with the screw terminal hardware, but no heatsink screws. Based on the packaging, I believe it is genuine new/old stock.
I had to order a heatsink separately, and it hasn't arrived yet. So at this point I'm just testing it with a nightlight. But it seems to work fine.
I have a question about the DC input drive. It's supposed to work down to 3V, and it works fine at my 3.3V. But that's driving a night light. If I put 10 amps through it, will I have to increase the DC voltage, or will the 3.3V continue to work?
Compared to what new/new Crydoms cost, this seems to be a good deal. That's assuming its age doesn't present any problems. Seems like it shouldn't.
Also, I find that the metal plate on the back isn't galvanically connected to any of the four terminals, which means I won't have to worry about the heatsink electrocuting anyone. I have grey thermal paste, which I believe is conductive, but if the plate is isolated that won't matter.
Anyway, I think this was a good buy so long as it keeps working. But as of now he has zero left to sell.
Edit: As of Dec 11, he's now showing more than 10 available.