The tag looks beat up but seems fine. I would need to see the vin to know if it falls in line with the tag.
Here is a list of things I would check.
1. Make sure the hidden vin matches the vin on the dash. - http://www.camaros.org/numbers.shtml#VIN
2. Look for all the areas of rust (since this was a vinyl top car definitely look around the front and back glass), floor pans, trunk area, rear quarter areas etc.
3. If you are concerned if the engine is original to the car or not. - http://www.camaros.org/drivetrain.shtml#PadStamps
4. Ditto on the transmission. - http://www.camaros.org/drivetrain.shtml#trans
5. Ditto on the rearend - http://www.camaros.org/drivetrain.shtml#axle
Honestly, if you just want a good car that is a great driver that you want to enjoy then I would just verify #1 & 2. These cars were meant to be driven regardless the rarity of them. When I finish my 3 they all will be driven as much as possible (weather permitting). If I were you I would spend as much time as possible reading over the info on this site before making a purchase. If you do not find the answers you are looking for just ask. Someone here will help you.http://www.camaros.org
I would at least have the seller send as many pics as they could of the undercarriage, hidden vins, and whatever else you wanted to view before wasting time to look at a car..