I have done a little research myself. There appears to be a 1913 date mark on it (S) and the London Assay Office stamp (Leo). It is upside down so i believe it was imported pre-1950. I cannot find any reference online to the sponsors mark which is an SA in a diamond shape. There is a well displayed series on numbers (like a serial number) and also a P stamped below the sponsor's mark. I thought this might be the makers mark but I don't know.
I couldn't get a clear enough photo, but, in addition to the main serial number, there are very feint groups of numbers engraved in multiple places around it. I am thinking this MIGHT have been done by successive owners over time. But I can't make out any real detail.
Anyway, any help would be appreciated. Like i said, I don't know much about my grandfather so I feel like this might be an opportunity to learn more about him. It was difficult to get information about him from anyone.
Thank you in advance!
J

