Hi Cul_Lector,
wt1 is 100% correct. It is a perfin from the Montreal office of the Canadian Pacific Railway Company.
This CPR perfin has been assigned Perfin ID# "C51" in the 4th Edition of the publication "Canadian Stamps with Perforated Initial", dated 1985, and then re-assigned Perfin ID# "C34" by BNAPS in the latest web based edition.
Your perfin has a rotation of '3', which means than it is readable from the front, and with a 180 degree rotation.
This perfin and rotation is quite common.
A down-loadable Canadian Perfin catalog is available at
http://www.bnaps.org/PerfinHandbook...Handbook.htm- stamporator -