Thanks for the quick reply.
Looking at the pictures you are doing a good job.
It should be 5 or 6 numbers long (yours I think 5), since the G numbers started at G17434. So there may be another number on the end. Please let me know, if you get the chance?
Either way, it's certainly G3XXXX, so the frame was built up into a bike Jan or Feb 1942. Which makes it one of the last prewar bikes, not fitted with Blackout parts.
Also, there was a hold on bike sales for a while immediately following the Pearl Harbor attack, which may explain the time lag between the frame being made, and the bike built up.
This bike is G35983, so I think has the type of chainwheel and guard yours would have had originally.
https://thecabe.com/forum/threads/need-some-westfield-columbia-bicycle-help.150891/
Best Regards,
Adrian