By the end of George's reign, in 1936, the bronze penny, which had felt lighter in weight compared with older coppers when the alloy was first used for it in 1860, was regarded as weighty and cumbersome, the heaviest bronze coin in circulation in Europe. The weight when in bulk caused problems for business; the London Passenger Transport Board received 6,000 tonnes of pennies, halfpennies and farthings a year. A reduction of size for the penny was deemed impractical, given the time it would take to recoin the 3,000,000,000 pennies in circulation, and because many automatic machines that took pennies would have to be reconfigured. The major response would be the 1937 debut of the brass threepence coin. This twelve-sided piece was introduced since threepence worth of pennies or halfpennies was heavy and inconvenient, and the silver threepenny bit was deemed too small.