The last book I have come across recently that has mention of the Leica in detail is by Jacqueline Winspear in the 'Maisie Dobbs' series. I have been reading 'A Dangerous Place' set in Gibralter during the Spanish Civil War.
The Leica is key to the whole plot. A local aspiring photo - journalist in Gibraltar is found dead with a Zeiss folder round his neck. In the climate of the refugee situation during the Spanish Civil War not a great deal of surprise is generated BUT along comes our heroine, young widow of the English aristocracy, who has lost a baby, and has British Security background('' They never let you go''), and an inquiring mind. She quickly finds a Leica in the undergrowth of the crime scene which contains a film revealing photographs of a Submarine - probably German - off Gibraltar.
The tale revolves around relations between the Rock, the Spanish conflict, the English Aristocracy, and relief workers and has no connections with the school of 'denouemont in the Library' with that sort of plot that we have all come to know and hate.
The writer provides a most humanitarian climax reflecting the views of both parties to the conflict and the support given from liberal supporters overseas.This could have degenerated into a 'Biggles' style romp over a well trodden background of Spain in the 1930's but grows in strength to reach a rather surprising end. A good read.