Wow. I hadn't thought of "LD" You're right of course. Looking at it more closely, I can see a depression in the center. What does the "M" signify and how was it used the find the exact date?
Here's what I know: First mark is "P&B" with an "L" and what looks like an "O" in smaller type. Second mark is a Lion Passant, so the item is sterling silver. Third mark is definitely a head, but is faint. I assume it is a Leopard's Head for London. Last mark is an ...