I cant find a stamping on my frame at all, but the first subframe crossmember in my 28 tudor has a five figure number with a prefix stamped on the left side.
The prefix is "F".Can you read the prefix? It should be the assembly plant from what I have read.
So that goes back to the question/theory of whether the F stands for "Fordson", the previous pre 1927 name of the Rouge complex, or Ford, Ontario (later called Walkerville and East Windsor Ontario), where Ford of Canada was.
Canada supplied most of the export models for the British Empire, whereas the Rouge supplied RHD for South America.
I say 'F' most likely means Ford, Ontario, but I am in the minority on this view.
I was told that only the Twin Cities plant stamped the rear crossmember as you show. My 28 Phaeton has "P8" and my 29 Tudor has "T0". The "P" stands for "Phaeton" and the "T" stands for "Tudor". The "0" stands for "10" leaf rear spring.
The "PU" on your frame stands for "pickup" and the "0" stands for 10 leaf rear spring. It looks like someone on the assembly line got carried away with the triple "0". If you look for your body number it will probably start with "TC" which stands for Twin Cities assembly plant. The body numer will be in the area where the driver's heel would be if he sits with his feet straight down.
The motor number is stamped into the frame usually about where the clutch pedal shaft is and I usually find it stamped near the vertical edge. It is probably stamped near the edge because the vertical edge of the frame would offer very good support for stamping. The body and splash apron needs to be off or at lease lifted a few inches in order to read the number.