William Singer, the brother of Charlie, Jackie and the late Tommy Singer, has used various hallmarks since 1972: SD (both side by side and offset), SDX, SDXX, SDV, S/D, all variations of the Singer-Dodge family shop hallmark. Tommy Singer has been credited with first using chip inlay in 1970. William began using the technique in 1972. Chip inlay is a method where cavities in jewelry are filled with a mixture of crushed stone, typically turquoise and coral, and epoxy resin. The piece is then polished smooth after the resin has hardened.