Leitz / Leica SBOOI 5cm Prototype Finder Viewfinder

Fully original factory prototype with accessory shoe on top, made in a very small series for testing and never went into production, in near mint condition with clean optics (the illustrated camera and lens is not included) - the prototype is illustrated in LHSA Viewfinder Magazine Volume 49, Issue 1 and a similar finder is illustrated in Paul-Henry van Hasbroeck - A History illustrating every Model and Accessory on page 265 (184b)