I can come up with one (possible) explanation and three (and a half) books:
"Rollei 35 Eine Kamera Geschichte" (Rollei 35 a camera (hi)story) since the German "Geschichte" means story as well as history, Claus Prochnow, best /most comprehensive and in color, German
"Rollei Report 3" Claus Prochnow, German
"Rollei 35 75 years" burgundy calf skin, came along with the 75years Rollei 35 classic, was sold seperately later. Rollei (probably compiled by Claus Prochnow), I think this one is bilingual, but I'd have to check.
The half one: Udo Afalters book on Rollei 35.
The engraved "Sonnar-writing" ring is just glued in place and comes off aesily ... when looking for a spare part you're in trouble, so maybe you go for the "Rollei 35 classic" spare part (without any lens number). Check here for pics:
http://lausch41.com/r351.htm