Although commerce did not require them in 1953, pennies which bore the likeness of Elizabeth II were minted in sets which were sold to the public, using an obverse design by Mary Gillick. One 1954 penny was struck, for internal Mint purposes. By 1961, new pennies were needed again for circulation, and they were produced in large numbers. The officials who planned to introduce decimalisation in the 1960s did not favour keeping the large bronze penny, the value of which had been eroded by inflation. The last pennies which went into circulation were dated 1967—a final proof set was dated 1970. The old pennies quickly went out of use after Decimal Day, 15 February 1971—there was no exact decimal equivalent of them, and the slogan "use your old pennies in sixpenny lots" explained that pennies and "threepenny bits" were only accepted in shops if their total value was six old pence (exactly new pence). The old penny was demonetised on 31 August of that year.