Keith,
My favourite Jersey, Heavy, which I have owned and put to heavy use for thirty years, is by Glen Gordon Ltd. I always assumed them to be Scottish. Have you any idea if they were one of the Leicester companies?
Dont reconise the name, so i consulted the oracle of past knitting companies in the uk " Skinners Hoisery and knit goods directory 1954" A wonderful old book i bought years ago.
The only company that might have made your Jumper is Gordon & Co. ( The Glen Glove and Hoisery Company) Union Glen,Aberdeen. Establised 1915 employees 400, Machines 150 circular 200 flat, product range; Woollen gloves,ladies and gents Knitted garments.
I also checked under trade marks and Glen Gordon is not listed.
Hope the above is useful.
Keith