This year, I’m a scout leader for the Pionniers (age 15-17). We made a “charter” they need to follow and instead of signing it, I made a wax seal for each of them with their initials. It made it seem a little more official.
I just engraved 1/8" white acrylic, and glued an acrylic “ring” to the back so they could easily hold it.
I bought some “sealing gun wax” online. It was then easy to do. I used some “pam” as a mold release. We then melted some wax, waited 20 seconds, and pressed the seal into the wax. It worked great.
I think they liked it. It’s hard to get a read on kids of that age.