From Lloyds Register of Shipping rules.
The + should be a “Maltese cross symbol and means that the ship was built under special survey
100 means it is a steel ship (will last 100 years) fit for sea-going service… Ermmmm, so about 12 years left then 😉
A means that the ship has been built into class in accordance with Lloyds’s Register Rules and Regulation, the ship is maintained in good and efficient condition.
1 means that the ship has onboard anchoring and mooring equipment in good and efficient condition.This last one is where the gorgeous bronze mooring bits come in.
*Big thanks to Richard Walker for help decoding *