A bit late to the party, but FWIW:

The name of the place where Crosman Canada was located in the early days is Dunnville - not "Dunnsville".

My own experience with the Crosman 150C pistols seems to be exactly opposite that of DT Fletcher.
Of all the 150C pistols that I have worked on over the years, the majority of which had come from the US, I have yet to encounter a 150C with the textured grip frame.
My own 150C was purchased in the US, and it has the smooth grip frame.

To my knowledge only the early 150s all had the textured grip frame, Then there was a transitional period with the introduction of the one-piece barrel/breech , where the guns could be found with either the textured frame, or the smooth frame. When the stock of textured frames were used up, the late guns were fitted with the smooth frames from that point onward.

I also recall reading somewhere, but cannot remember where at the moment, that all 150C guns were made exclusively at the Fairport factory, which seems supported by the fact that all the 150C guns bear the Fairport markings.