In the old currency (before Britain turned to decimalisation in 1971) half a crown was a single coin worth two shillings and sixpence (one eighth of a pound, or twelve-and-a-half pence in new money). In the North East the coin was sometimes referred to as 'half a dollar'.
The other pre-decimal coins and notes current in the late 1950s were:
Halfpenny; in practice the smallest coin of legal tender. (Farthings, with a wren motif, were still technically legal tender until 1960, but were already a curiosity in the late 1950s and were virtually never spent in the shops.) Children frequently used halfpennies to buy ha'penny chews, or even two farthing chews.
The old penny, 1d. Known as a 'copper' for its colour and main metal. Around that time, bubble gum machines appeared outside some general dealers, offering a ball of bubble gum for a penny dropped in the slot. Twist a handle at the front, your penny disappeared, and a ball of gum dropped down into the collecting chute. If you were lucky, you might get a plastic lucky charm as well, or two bubble gums would fall through instead of one; if you were unlucky the door of the chute failed to hold the ball and it would drop down onto the ground at your feet.
Threepence, 3d. Usually referred to as a 'thrupenny bit' it was twelve-sided and made of a warm bronze-coloured nickel-brass, though it was still possible at that time to come across smaller silver threepenny pieces. The middle classes put these in Christmas plum duffs; the working class mothers of Ashington would wrap them (or other small coins) in greaseproof paper to put in the middle of scones laid out for children's birthday parties.
Sixpence, 6d. The equivalent of two-and-a-half-pence in new money, this small silver coin was colloquially referred to as a 'tanner'. Around this period the sixpence could purchase a big bag of chips, and people would often ask for a 'fish and six' at the chip shop. Brides would traditionally put a tanner into their left shoe on their wedding day.
Shilling, usually written as 1/-, and colloquially referred to as a 'bob'. As a fund-raising venture each year boy scouts and cubs would be busy with 'bob-a-job week', earning a shilling a time for doing small jobs and errands for their neighbours. (Or not so small; at the age of nine, the author was asked to weed a large garden for which he was paid one bob.)
Florin, 2/-. No-one in the 1950s ever called this coin a florin in everyday life; it was always known as either a two-shilling piece, or a two-bob bit.
Crown, 5/-. Theoretically still legal currency in the 1950s (the last one was minted in 1965) the crown was virtually unknown in everyday currency. These large coins were generally reserved for commemorative gifts, often presented in boxes. The author still has one he was given as a toddler for Queen Elizabeth II's Coronation in 1953.
Ten shillings, 10/-. A reddish-brown banknote, valued at half a pound, the equivalent of 50p in decimal currency. Usually known as a 'ten bob note'. It was withdrawn to be replaced by the 50p coin in 1969.
Pound, £1. The base unit of currency, available in the 1950s only as a note, and now available only as a coin in decimal currency. The pound was commonly called a 'quid' in the 1950s. Larger banknotes was also available in the 1950s, but it was rare for working people to see one larger than a five pound note.