In the British Isles small denomination banknotes are quite unusual, a likely result of denominations of less than 20/- having been banned by Act of Parliament in 1775. The next 40 years did see a few provincial issues by banks and businesses with denominations ranging from 2d to 15/-. Based on Roger Outing’s catalogue (England and Wales, not counting skit notes) there are just 26 notes issued for 5/- or less and the number increases to 51 when notes for less than 20/- are added. This article was prompted by the acquisition of a One Shilling note issued by J. Wilkinson of St Clement St. in Ipswich in 1797 and brings together what I have found that has already been published. The conclusion is that the name John Wilkinson is a very challenging name to research and his address was in one of the poorest areas of the town.
The Banknotes issued by J. Wilkinson of Ipswich in 1796-7 – Gary Oddie
BNS Research Blog 
Another interesting article. Have you researched the names on the back, presumably the owners of the note as it was passed from hand to hand? Could the date for Rob. Ralph? be Feb?