Hi Brian,
As coincidence has it, I have been undertaking similar research and the answer so far is 'no'. I'd be interested to see if there are higher serial numbers than those quoted. The highest number I am presently aware of is in the J30200s and this is believed to be an 'Anniversary' model from 1942.
Not sure if the researcher is aware of when cylinder stampings changed from the prewar style to those commonly seen on post war Juniors? The barrel was also shortened around this time. I am aware of pistols with the 'later' features in the J28000 range but understand the change came earlier. It would be good to pin it down.
Kind regards,
John