A series of studies assessed the extent to which different versions for a #xA3;1 coin might be confused with existing coins. The first experiment demonstrated that a milled coin of 22 mm diameter and 2*8 mm thickness would be confused with the 5p by touch. The experiment was repeated with a coin 315 mm thick and the error-rate was greatly reduced. A third experiment compared the two different thicknesses directly, and also included a 3-15 mm coin with a different edge (interrupted milling) for comparison. Both the thicker coins produced similar performance, which was again better than that achieved with the 2-8 mm version. In experiment 4, three different thicknesses of the #xA3;1 coin were presented for identification to a sample of blind and partially-sighted subjects. The thinnest version (2-7 mm) was frequently confused with the 5p, but the thickest version (3-1 mm) was rarely confused. Finally the thickest version was included in a study in which sighted subjects sorted coins in dim light. Under these conditions there was again some confusion between the #xA3;1 and the 5p.
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