The 1971 New Penny, featuring Queen Elizabeth II, is significant because it marked the transition to decimalization in the United Kingdom. It replaced the old system of pounds, shillings, and pence with a simpler decimal system, paving the way for modern currency in the UK. The New Penny was the new unit of currency, with 100 New Pence equaling 1 pound. This change streamlined financial transactions and brought the UK in line with other decimalized countries.