The British decimal fifty pence coin (often shortened to 50p in writing and speech) is a denomination of sterling coinage worth of one pound. Its obverse features the profile of the current Monarch since the coin's introduction in 1969. , five different royal portraits have been used.
there were an estimated 920 million 50p coins in circulation. The coin has proved popular with coin collectors leading to numerous differing designs for both commemorative and circulating coins.
Fifty pence coins are legal tender for amounts up to the sum of £10 when offered in repayment of a debt; however, the coin's legal tender status is not normally relevant for everyday transactions.
History
In 1967 the Deputy Master of the Royal Mint approached the Decimal Currency Board to ask for their advice on the introduction of a new coin. The 10-shilling note then in use was lasting only five months and it had been suggested that a coin, which could last fifty years, would be more economical. The problem with this was that all coins are arranged in "tiers", each coin in a tier having the same weight-to-value ratio so that a bag of mixed coins could be weighed to ascertain the value so long as they were all bronze, all silver, etc. Each coin was identified within its tier by its size and each tier had to be capable of being identified by sight and touch. This was achieved in the then-existing sets by the use of different materials ("bronze", "brass" and "silver") with the bronze coins having plain rims, the nickel-brass threepenny bit being 12-sided and the silver coins having milled rims. If the 10-shilling coin was to be made in the same tier as the silver coins it would have to be twice the weight of the Crown (then and now only in use for commemorative coins) and it was generally agreed that that would make it very unpopular and expensive. It would therefore have to be in a new tier of its own.
The Mint could not find a suitable metal which was sufficiently different in colour to the existing coins and which would not tarnish. This last point was thought to be important because the new coin would be the most valuable coin in general circulation in the world (). It therefore had to be a different shape; various methods had been used overseas to overcome this problem but none were without drawbacks. A hole through the coin did unacceptable things to the Queen's head (a legal requirement on British coins), and wavy-edged, flat-edged or square coins could not be used in the coin-handling machinery which was then coming into increasing use in industry, banking and vending. To be used in a vending or sorting machine a coin would have to roll under gravity and be capable of being measured without being presented in a special way; in other words it needed a constant breadth at whichever angle it was measured.