Copper Sandwich was actually invented by Al Koran c. 1948 and was originally performed with a matchbox and the gimmicked coins of the time (see New Pentagram April 1973, pg. 13). Eddie Gibson refined it, using more advanced coins, and created the brass box for an even cleaner and more amazing penetration.
This is the original version of Copper Sandwich with UK coins and compares with this later version using US coins.
It is a great effect which is easy to do and leaves no clues as to how the penetration occurs.
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