Looking at the picture again, it appears that the part with thistles etc might possibly be a stock item, with the central disc with the initials attached to it. Is this a trick of the photo, or is it really like that?
The mention of Kings Lynn gives me an idea. How about something like Lynn Seamen's Sickness Savings Club, with the dates showing when he'd paid his subs for? With that on his watch chain, if he was taken ill he might be able to get treated straight away, without any enquiries as to whether he could afford it. Just a thought... (I've no idea if there was such a club, but there were friendly societies and others which covered their members' medical bills.)