Leon, I am agreeing with you now that the Fro-Joys are tougher to authenticate, especially compared to the Geo Ruth Candy cards which Ive followed much longer.
On the Fro-Joys..... the more I looked into them last night, the more I was confused, many slabbed examples I believe are not authentic and I just cant trust them. The only one I trust is that sheet that was found in original envelope with the premium (all framed together).
Before this thread was brought up I concentrated on the Fro-Joy Portrait card as thats the one I was seeking to buy and I think I still can tell the difference on it. But the others I dont have characteristics to look for yet.
Here is a scan I just made using the sheet card found with orig envelope and the larger card posted above.
scanner setting may have something to do with the contrast , but Im sure if they were next to each other it would be easy to tell them apart too.
left card is a known authentic card
On a slightly related note... I have dozens of scans of the Geo Ruth Candy Co. cards (slabbed, raw, in 1930s scrapbooks, etc.) and there are 3 different types, with 2 different croppings of the photos. 1 type show more image on one or more borders while the other show more image on other borders. below, example of the chase card #6
I will one day make comparison images of the other #s too.