doppelgängsters
Here is an interesting idea for signature dupes on a playing card. You end up with a convincing signed duplicate card that you can later switch out for examination. The idea is in two parts: prep and premise. Once you’re prepped, you’ll have created a premise that this card lives in. I’ll also say this before diving in- this is not a “test condition” type of thing. So, under scrutiny, it won’t work. But I think it’s an interesting concept that costs only a few minutes of your time, and can go pretty far.
You’ll need two duplicate spot cards. I’d go for 3, 4, 5, or 6 so there’s a good balance of space and pips. Probably also use hearts or diamonds since black sharpies are used most often. Face cards are no good.
Here’s the idea. On the first card, scribble a bunch of different initials in different handwritings, orientations, sizes, and weights. Nothing too large or too jarring, and also not too many. You’ll want to get enough on there so it’s not easy to remember what every single one looks like, but not too many so it looks super cluttered. Leave some space as though more can be added later. I think the same color would be best if you already have different thickness, but maybe there could be one.. maybe two in different colors. Don’t want it to look too distracting though, but an accent could be nice. The point is to make every initial look and feel random- as if you’ve used this same card previously.
Once you’re happy with the first card, duplicate the exact same thing on the second card except for one of the initials- leave that space blank. That is the space where you’re gonna have your spectator sign their initials. A couple things to keep in mind, this space shouldn’t be outer most- near the edge of the card, nor should it be centered. You want it to be kinda lost so people will assume that it’s there at a glance.
Here’s a quick example (it could be better, but gets the idea across):

You probably get it now. The first card is the pseudo dupe. The second card is the actual signed card. From here, I’ll leave it up to you. But the idea is simple. After the card is signed, it can be switched out for the pseudo dupe and ripped up, while you have total control over the actual signed card. You can flash the dupe too and all the other initials will help hide the pseudo initials. You can also plant the dupe somewhere, and vanish the actual signed card at some point. Reveal and fetch the dupe (probably have either you or someone who didn’t sign the card - so they can’t identify the initials) then on an offbeat switch it back for the signed card. Lots of options here.
This is probably best for social situations. It feels less set up to re-use a signed card. I mentioned a premise earlier- this is part of the presentation that goes with this card. The card itself is one that you use for “this trick”, whichever trick you’re doing. And you’ve done this for a bunch of people already. The initials act as a tally kinda.
In a social situation, like at a bar for example, you can say you’ve been doing this throughout the night, and let them assume that the other initials belong to other patrons from earlier.
You can also have a second space on the real signed card and reuse the card. Just make sure you remember to secretly fill in the same space on the dupe as well after the first trick. And don’t do those two tricks back to back. This can be cool because if the first person is still around, they’d be like “oooh yeah! I did it too!” It’s always exciting when someone gets to share a magical experience. You’d obviously do another trick, but that’s one way to get multiple uses out of the same card.
Lastly, see if someone else asks about the card first. Just have it in the deck and do other tricks. They will for sure see it at some point. And if someone asks, you have a great lead in. Just make sure it’s a super dope trick.