Contradicting Marks?

British Hallmarks indicate:

1. City Mark - Leopard (NO crown): 1822 - present

2. Silver Standard Mark: Lion = .925 Sterling

3. Date Letter: 1821 or 1781

4. Duty Mark: King George III 1786 - 1821

5. Maker's Mark: Unclear (FD, FB, or ID, IB) ?

Done