[drcy]

What Pete said.

You can make a fair judgement by examining the photopaper. If it is toned, or at least off white, and fibery/matte on back and all dried out and otherwise seems old, that's a good sign its old. Also, almost all modern paper fluoresces under black light, often has a plasticy/smooth back as its resin (plastic) coated and the stock is much whiter (often snow white).

As mentioned, a modern photo card made from the original negative isn't quite the same as a regular baseball reprint or fake, and might be worth something anyway to go along with the stand. Obviously, baseball card collectors desire the vintage 1930 version and a modern version by itself (sans stand/kit) will have little value, but it would be like making a modern photo made from that Conlon glass negative you won at auction to display with the negative. The Ray O Print kits (and stand) are worth a lot more than the actual card, even if the card is vintage, just as the value in that Conlon display would mostly due to the negative.

15, 20 years back a dealer had plethora of the complete Ray O Print sets in very high grade-- where most kit photo card singles are tough--, which made me think someone had made modern versions from the negatives. But old versus new photo paper is usually pretty clear and you can judge card by card.

If someone's a nervous or unsure about the issue, he can invest his collecting money in the kits (envelope, negative, stand or frame), which you will see for sale and auction. No one's reproduced the kits and they're highly collectible themselves-- with or without an accompanying card.