Never heard of or seen these before, they look freaking sweet What do you think of these? https://rover.ebay.com/rover/1/711-...8YAAOSwpwZdAnRJ:sc:USPSFirstClass!94025!US!-1
I've owned this one for years. These pieces were not used to smuggle drugs; they were used to house photos and the like. This modification was also done to Columbian half dollars.
There was actually a booth at the exhibition that would do them for you right there. You would drop off the two coins (it took two, one for each side) and come back later and pick up your locket. I don't know what they charged to do them. But when you consider the halves cost a dollar apiece I'm sure the cost was significant for the average person.