Further to Ian's observations, if the motor is a 1928 era motor the number letter prefix will be EL, is the "F" very clear on your engine? the 1202 would place it late 28 or even 29. The frame, as Ian says does look OC, if you do have your numbers the right way round the FL could have become blurred all OC frames we know about have only three digits, I suspect the D you have as the last character is the remnants of the Douglas trademark a D superimposed with a K, (See Doug's vivitar!!)
Any chance of getting a photo of both posted? I know the frame number is very difficult and often unclear in itself. If you really cannot get a photo you could try taking a "brass rubbing" with thin paper and a soft pencil, these scan rather well!
Good luck, sorry wheels are rather like hens teeth!!!