That Unimat looks cool. I wish I had something that I needed to make to justify buying one. At least I now know that it exists. Thanks for the heads up.
http://www.youtube.com/watch?v=LZe3E3rpRTk

Hey, don't call/email people in the know of expanded shells, to reveal their secrets. They get pretty *)*)*)(*)(*) upset about being asked.
I guess this is a trade secret. There are actually several ways to make them, but they all take a bit of time and expense.

@ tabman the very first Johnson coins were made by Sheldon Atterbury on a small 6" craftsman lathe. (i saw it in his garage). He and C Johnson took the prototypes to Sam Laport (who later bought the business and became Johnson products). Sammy Laport used a Logan lathe with collets to hold the coins (made them special). The expanded shells were made from all silver coins using a spinnning process to expand the coin as it was held (barely grabbed) by the outer edges. He also ran the lathe in reverse for this process (am not sure why, but I believe it was to get a better finish inside). I was there.

I have a few early sets of coins that were made by Sheldon "Shell" Atterbury using this process in my collection.

I have a locking $1.35 trick, a half dollar to paper dollar, and an effect called "Quarter Attraction".

Each of the sets are made using 1964 silver coins.

The coins lock using a "press" type release that does not require the use of a bang ring.

These coins are apparently rare as when I contacted Johnson Products to inquire about them, they had not heard of them.

The instructions list Johnson Products address as P.O. box 734 Arcadia California.

James Riser use to have instructions on making shells on his site...
https://www.jamesriser.com/Magic/JamesRiserMagic.html