This is a can of daub that was originally sold by the KC Card Co, under the brand name Chink Ink, which is undoubtedly not a politically correct term, by today's standards, but is used here simply because it is the original name.
There is nothing spectacular about this gaff. It is just a can with some daub inside. But the ad in the Blue Book gambling catalog describes this as a prop to be used against three card monte hustlers. Why would it work better for three card monte, than any other card game where one could gain advantage by marking cards, is not clear from the Blue Book description.
Although this gaff is advertised as a gaff to be used against a three card monte mob, it should be noted that winning at that game is a pipe dream. Three card monte is not even a legitimate card game, it is just a swindle, and as all swindles go, it is played with the specific purpose to steal money form suckers. In theory, a sucker may be able to lay his money on the winning card, but getting paid is an impossibility. These swindles are always mobbed up and if the sucker happens to put a wage on the right card, his wager is immediately followed by a larger wager, placed by one of the team members posing as a player. The moment the larger wager is declared, the operator announces that only the highest bets are accepted and immediately turns the winning card over. This actually helps the mob because it gives the appearance that players can win and that they get paid. The sucker may complain that he was the first to place a bet, but the operator now makes it clear that the "house" only accepts the highest bets. This actually preps the sucker for a kill, as he is frustrated that a winning bet just slipped through his fingers. Now the sucker is prepared to bet big and the mob will keep out betting him until he places his wager on the losing card.
So, the moral of the story is that no one ever gets paid in three card monte.
If we take all this reality into consideration we can only come to one conclusion: that this product was basically a sucker item. Many of the gaffs sold by the KC Card Co, and other crooked gambling suppliers, were in fact just sucker items. Real card cheats and hustlers hardly even need or use any of these gaffs. The gaffs were basically just novelty items sold to the masses, to make a buck, and to give the suckers a false sense of security, making them believe that they were in the know. Now when the original crooked gambling supplies are out of biz, these gaffs are desirable to collectors. In fact, they are fascinating items.