GREAT BRITAIN. Copper-Nickel Pound Pattern Trial, 2015. Llantrisant Mint. Elizabeth II. PCGS AU-58.Mintage: 23. This bimetallic trial piece was produced in early 2015 and distributed to companies to calibrate vending machines which explains the surprising evidence of circulation present. Inscribed with "trial piece" on the reverse, this nearly unheard of example is a piece that will expand the cabinet of British collectors.