When did the old pound coin come into circulation?
The British one pound (£1) coin is a denomination of the pound sterling. Its obverse bears the Latin engraving ELIZABETH II D G REG (“Dei Gratia Regina”) F D ("Fidei defensor") meaning, “Elizabeth II, by the grace of God, Queen, Defender of the Faith”. It has featured the profile of Queen Elizabeth II since the original coin's introduction on 21 April 1983. Four different portraits of the Queen have been used, with the latest design by Jody Clark being introduced in 2015. The design on the reverse side of the current, 12-sided coin features four emblems to represent each of the nations of the United Kingdom—the English rose, the leek for Wales, the Scottish thistle, and the shamrock for Northern Ireland—emerging from a single stem within a crown. 
When did the old original pound coin come into circulation?
21 April 1983
One pound (British coin)
No context provided
When did the old pound coin with a portrait by Raphael Maklouf come into circulation?
1985
No context provided
When did the old pound coin with a portrait by Ian Rank-Broadley come into circulation?
1998
One pound (British coin)
https://en.wikipedia.org/wiki/One%20pound%20%28British%20coin%29
Between 1985 and 1997 the portrait by Raphael Maklouf was used,[15] in which the Queen wears the George IV State Diadem.
One pound (British coin) Design
Between 1998 and 2015 the portrait by Ian Rank-Broadley was used,[15] again featuring the tiara, with a signature-mark IRB below the portrait.
One pound (British coin) Design
The British one pound (£1) coin is a denomination of the pound sterling. It has featured the profile of Queen Elizabeth II since the original coin's introduction on 21 April 1983. Between 1985 and 1997 the portrait by Raphael Maklouf was used, in which the Queen wears the George IV State Diadem. Between 1998 and 2015 the portrait by Ian Rank-Broadley was used, again featuring the tiara, with a signature-mark IRB below the portrait.