LONDON, Royal Mint, Plating Trials (4), c. 1980, in conjunction with Texas Instruments, in cupro-nickel, rev. 1 in wreath, 4.60g; in iron, rev. 7 in wreath, 3.84g; in brass-plated steel (2), revs. 8 in wreaths, 4.14g, 4.10g, all 23mm (Tansley –) [4]. Virtually as struck, rare £100-150