belly numbers

[glaser 31]

I have 2 cases laying, 1 with raised letters is has the belly numbers U9
I dont know year.its a twin, the engine numbers cant be read more thats why I hope the belly numbers could tell what year its from.
Then I have 1 with the belly number K4,it has casting number 21 inside,
but I have know idea of year and model

[Sargehere]

"???" Sounds like nothing of this world. PHOTOS, photos, please.
Wasn't Dale Walksler's experimental 1936 Sidevalve Big Twin U-motor numbered something like that? We'll need some pics, Glaser!