Design Considerations and Proposals for Compatible U.S. Subsidiary Coinage

Coin silver, as used in U. S. subsidiary coinage, is made of an alloy containing 90 per cent silver and 10 per cent copper. During the last decade, it has become increasingly evident that the availability of this alloy for the continued production of coinage is jeopardized by an increasing unbalance between the demand for, and the supply of silver. The involvement of Bell Telephone Laboratories in this issue results from the use of 5, 10, and 25 cent coins in public telephones. In view 493 .494 THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1906 of the possible change in subsidiary coinage alloy, it became necessary to identify the functional properties of coins in their various applications and to specify accurately those properties which are essential to maintaining an operationally compatible coinage system. To this end, work was initiated on a study of coin properties and compatible metal systems for U. S. subsidiary coinage. This paper records (i) the results of an investigation of the permissible deviations from the present coinage system for compatible performance in coin chutes, (it) proposals for changes which represent improvements in the present coinage, and (in) the analysis and description of various metal systems which could be employed. This information has been discussed and confirmed with various representatives of the vending industry and conveyed to the U. S. Mint and the Battelle Memorial Research Institute, consultant to the Mint, for their use. I I . COIN CONSIDERATIONS