Great Britain KM 959

I have the year 1988 of this coin. Could you include it in Numista?

You must have a counterfeit. The only 1988 £ coin was this one: https://en.numista.com/catalogue/pieces7405.html .

https://en.numista.com/catalogue/pieces1388.html
https://en.numista.com/catalogue/pieces1392.html

  So that first link is the mentioned KM# 959 which is the UK 1 Pound of 1989 date.
As it happens I have a 1989 pound the other day, and to agree with the above reply, mine is also a forgery.
So that 1989 date should have the Scottish thistle on the reverse, but mine has an Oak tree with crown, which is on the 1987 and 1992 coins KM# 948 reference (second link).
  The edge lettering DECUS ET TUTAMEN does match the reverse image, but the 1989 date should have NEMO ME IMPUNE LACESSIT on it. That lettering on mine is rubbish, so is easily a forgery indicator.
  The counterfeiters got the  Medal alignment ↑↑  right, in that both obverse and reverse are vertical.

The counterfeiters are amazing with some of the detail and even sometimes with the edge lettering...but there are always a few tell tale signs.

https://en.numista.com/catalogue/pieces1390.html

  Finally, within a few days of that in my change, I got another forgery; I do not see any for ages then two come along at once. This 1996 one is better - the obverse and reverse both match the 1996 designs, the Medal alignment ↑↑  is also correct, as is the edge lettering  DECUS ET TUTAMEN  but again is poorly made. That and the reverse image is weakly struck. Altogether not a bad attempt.

I always find there is a small unstruck place on a forgery and quite often they make them a little dirty to cover it up!