Trail Double Circle Machine Cancellation

During the George VI period, the Trail, B.C. post office used an unusual double circle machine cancellation which lacked a  dater hub. Pete Jacobi referred to the cancellation as the "Trail Nude Cancel" in  his 2004 BNAPS Topics article Postal History, Trail (B.C.) .

I recently acquired a cover with the nude cancellation which is shown below.

Unfortunately there was no enclosure to determine when the cover was mailed. The upper limit date for this cover is April 1, 1951 since the domestic printed matter rate was increased from 1 cent to 2 cents on April 2, 1952.

I recall that this cancellation had been discussed elsewhere but I am unable to locate any other reference. Perhaps a reader might be able to shed additional light. [philcovex@gmail.com].