Here is what I find about this plate variety:
Because I find it from the first paper to the NOP paper, I estimate that the first plate was used from 1936 to 1948. I do not find it on the later papers (2C to 1Ls), and therefore estimate that there was a second plate used between 1949 and the mid 1950s.
The specimens I find:
On cover postmarked 1943.
NGR, dated 1947
NOP, dated 1949?