MAMIYA - Seikosha Mamiya Shutter Changes

Technical document issued by Mamiya Osawa Camera Service Inc. detailing design modifications to Seikosha shutters fitted on Mamiya rangefinder cameras. This service manual provides a complete parts inventory of internal shutter component changes affecting both chrome and black shutter variants available for Mamiya C camera systems. The document covers critical modifications to the slow speed governor, main drive spring, and speed ring assemblies—components that are not interchangeable between earlier and later production runs. It clarifies that the standard slow speed governor 1103000 (#35) remains unchanged and will continue to be available, while pin-equipped variants designed for press focus mechanisms are being discontinued. Detailed technical illustrations show shutter blade configurations, internal spring and gear assemblies, and mechanical layouts across three primary shutter combinations, with diagrams clarifying blade orientation when viewed from the front toward the rear of the camera body. Part numbers and correct assembly specifications for each shutter model are identified throughout, making this an essential reference for camera technicians, repair shops, and service professionals maintaining and restocking Mamiya C camera shutters. The workshop manual format allows technicians to cross-reference components during disassembly and reassembly procedures.