OSEF e.V.
This is an abbreviation for Ostsächsische railway enthusiasts, in german OstSächsische EisenbahnFreunde.
With the establishment of a centralized register of railway vehicles (Eisenbahnbundesamt) each vehicle owners a multi-digit combination of letters is assigned. The previously used OSE was unfortunately already taken, so that we now intend to act with OSEF not only in official business.