Year letter Gothic C for 1862, your image of year letter is upside down. Minerva Head with the regional assay office letter M for Schoonhoven. Lion passant above 2, 2nd standard silver 833/1000.
The maker's mark
Perhaps AD81 in square for Jacobus van Dam, started 22-5-1849, stopped 1888. His brother Huig van Dam worked for him as a servant and engraver as of 1-5-1873. Jacobus van Dam made small silver work, including silver (bible) locks, miniatures and boxes. He also traveled with his work to other market places.
Peter.
Source; Zilversmeden van de Stad Schoonhoven by S. A. C Begeer, E. Hak & L. Linhart-du Cloux