|Note_en=Published also on: N. 42 (1930-10-19). Advertising for the [[Duofold]] model, showing a set in marbled celluloid, and the desk pen conversion. | |Note_en=Published also on: N. 42 (1930-10-19). Advertising for the [[Duofold]] model, showing a set in marbled celluloid, and the desk pen conversion. |