Toronto. Leitz was determined to see the tiny Leica camera succeed as a “do anything bigger cameras can do” camera. For copy work, a focussing stage was offered. The stage swapped the Leica with a ground glass viewer for focussing. The most common viewer for the ground glass was the 5x LVFOO.
In the very centre of the ground glass is a clear glass circle. The LOOWH and LWHOO were 30x magnifiers that allowed an aerial image to be viewed for extra precise focussing.
The LOOWH came to market in 1936 with a slide-in ground glass mount. Two years later the LWHOO was marketed, this time with a bayonet mount that would also fit the slide-in ground glass mount. Some books suggest the transition to the new telegraph code word of LWHOO was earlier, around 1936. There seems to be no record of when the manufacture of either 30x magnifier stopped.
I picked up my LWHOO back in November of 1980 from PHSC member Pim Schryer. The signature (Ernst Leitz Wetzlar) suggests post war manufacture.