Try not to think of it as dirt rather as patina and, like the surface on 18th century mahogany created by generations of housemaids and their polishing kits, leave it well alone.
The badge is of great interest to those curious about the Thames which as almost everybody interested in London, or Londinium as the Roman named it.
The absence of bridges, the opposition to them being built, both as navigation hazards and for aesthetic reasons, made the role of the waterman or wherryman vital.
A quick look at the remnants of the original Roman bridge — considerably inland from today’s river banks reminds us that the city was an estuary town built in marshland stretching for miles.
The first stone London Bridge – the one with all those houses and stores piled on it was built on caissons making the water between them run so fast and at certain tide times drop so fast and so far, dozens of waterman died every years just getting between its arches.
Here’s HV Morton writing in 1939: “The Thames… Everything begins and ends with that river whose ebb and flood is the pulse of London. I saw its waters below me, dark, oily and swift, and I began to think of its nineteen centuries of history, a long time for men to have lived in the same place […]. To each generation, the Thames, coming freshly from the sea and returning again to the sea, might be said to symbolise life itself.”
Shortly after he wrote this, most of the docklands were destroyed by the blitz and the waterfront of the busiest port on the 19th century world disappeared.
My own London forebears were intimately involved in the river and the men that worked on it both as wherrymen and dockers.
A piece of silver I would love to see, but never will, is about the size of your disk. It’s the small .925 plate that was put into the skull of a river man by my maternal GG uncle who performed the first brain surgery anybody managed to survive at St Barts.
CRW