Classic example of a hand-made marked deck. The ink used to match the card's back color was excellent - I can't see a difference in shade.
Some collectors would pay money for them, though how much, I don't know for certain. Have you tried pricing them using the Hochman's Encyclopedia? The pricing guide would give you a rough ballpark for what such a deck would trade for these days. Some card collectors would value them lower for the markings, while others might actually value them higher as gambling ephemera. If you had the original packaging and the missing joker, that would increase the value, as would having the cards in pristine condition - which clearly they aren't as I'm sure they've seen a lot of use over the years. Lastly, if the claims about the deck's origins as belonging to a gangster are true, there's a chance that if these claims could be verified and documented, a collector of such memorabilia might pay a higher premium for them than a card collector would.