You need to see more pictures... Close up pics of the neck and headstock. Then, the neck needs to be pulled off and the end photographed. As well as the pickguard and underside of the electronics. They should have things stamped or initialed with the dates. I would say this is just a frankenstein of pieces. It looks like a 50's or 60's Strat neck, but not necessarily actual (could be a reissue...which isn't a bad thing...or a copy, which might be a bad thing). However, it's totally unique and pretty damn cool looking, if you ask me. At $500, it could either be a steal or a little overpriced, depending on what parts and the condition. You just simply need more to go on.
It could be the real thing, or it could be someone trying to take you for $500 with a knockoff. No serial number? If it's old enough for that to be a legit statement, then it's probably worth enough to justify having an expert look at it.
If you can't get him to pull it apart and photo it, offer something like $250. Try and bargain him as low as possible to give yourself some budget to make repairs or replace parts if you want it to be playable. But, you may get lucky and it may play and sound amazing. It's a crap shoot, really.
One more thing. Don't be too impressed with the faceplate, if that's all he's got to go on. Who cares about a 1960 faceplate on some knockoff. In that case, I would just ebay the faceplate by itself, and mod the thing to my liking. If it's truly vintage, that's obviously another story.
I checked it out today. It looks old, and actually plays good. I noticed that the tuners looked like they were from like a classical. It looked very aged, like it would be from that era no matter what. So I should ask him to look under the neck for a serial number?
I would call myself well educated, but definitely not an expert. I don't think there's any way that's a 50's or 60's paint job (maybe late 60's, but probably not). However, like I said, I think the paint job is awesome. It looks 70's to me. Honestly, I'd just counter offer and try to get it as low as possible. If it were really vintage, in any way, it's extremely rare and $500 is ridiculously low.
Absolutely no clue. There's were an expert would have to appraise. There are a lot of variables. It's so modified that I don't think it would exceed $10k, but wouldn't be surprised if it appraised at $5k or $6k. But, who knows. It's so original, I'd probably just keep it and play it. It'd be a kick-ass guitar for a punk guitarist (visually speaking). If it has a nice tone and feel, it'd be a good signature piece for a lead guitarist of any genre.
I am not an expert on that matter, but I think it's kinda funny how it was nearly impossible to find vintage instruments in the '90s and now you can spot them everywhere. Personally, I wouldn't buy it.

It got deleted, I don't think that's a good sign.