https://imgur.com/a/CZUdzQt

I have recently acquired this air pistol which I believe is a Webley Junior. The serial number is J19881 and it looks like 881 stamped on the end of the cylinder. Apart from 'googling' I know nothing about these pistols and would like to know more. Is there anyone who can give me a rough guesstimate of its manufacture date, and I hazard a guess that the screw and nut holding the handles on is not original unless someone tells me different! Does anyone know where I could get a breech seal as the original looks fairly distorted?
Many thanks for any info here.