Very simple to make.
1. Sacrificed pen drive
3. Plastic putty
4. Some paint
1. Box cutter
2. Small flat blade screwdriver
4. Q-tip for paint brush
Start with an ordinary pen drive. Carefully split the plastic to retrieve the electronics, a box cutter and small flat blade screwdriver will do the trick nicely.
Epoxy is a natural insulator. If your pen drive core is an open circuit board, completely epoxy one side of each coin first and allow to dry. Then apply some epoxy on both sides of the circuit board and allow to dry. This will insulate the electronics from the metal coin. Then sandwich the "insulated" electronics with more epoxy between the 2 "insulated" sides of the coins and allow to dry. If your pen drive core is encased with a metal housing, just epoxy the coins to the housing.
I then went to our recycling center and found some plastic putty. Mixing up a small batch, I filled in the space between the coin edges, allowed it to dry and sanded smooth with sandpaper. That Durham's stuff is great, I use it for several filling applications.
Finally, the recycling center had some gold paint, I thought it would look pretty cool. So I painted the plastic putty gold using a q-tip as a brush. I do lots of computer repairs. Customers give me lots of compliments.