Sorry, yours question and basic calculations aren’t very clear. Please read also the basic information on Plated available here: http://www.925-1000.com/a_platenumbers.html" onclick="window.open(this.href);return false; There are the basics sufficiently explained. Plated cutlery include ‘salt spoons...
Service ‘Grossmutter’ [Grand mother] Bruckmann-Model series 10283; in production since 1850 until 1973. (Source: Company’s catalogue ‘Album 64’, plate 9, number 10283.)