Hi Kolo,
The frame looks very much like the one on my OK Supreme !! (1931 model B) the same cycle parts were used on the ohv model G/31
Can you find a number on it?
the twin down tubes, loose clamps on the tubes and the bolt in the lug just under the solid saddle mount
look the same as far as I can tell from your pictures
THe mudguard is different but looks like the one in the pic of the model L/31
theres a catalog for sale on ebay at the moment, with all the models shown for 1931 number, 370509367914
It seems that OK fited different forks/ mudguards to their models at different times during the early thirties
so it is hard to identify specific model or year form just photos,
The VMCC in UK should be able to tie down the year from the frame number
Later 33/34 or so frames do not have the twin tubes from the saddle to the bottom rails, they have a short
single tube,
Search here on the forum for OK Supreme, there are some pictures and more topics
All this is my best guess and may turn out to be bulls**t
LOL
Hope this helps
Regards
John