Here are two cool 45 RPM disc variations from 1952 and 1953. Each one has a different style of "optional center" which allowed the owner to play the disc on a record player with either an LP/78 spindle of the newer RCA large hole spindle. The centre could be punched out with a bit of manual force and there were some directions printed on the accompanying stock sleeve. How many of these have survived today without the centre punched out ? Capitol of Canada was clearly experimenting with the new 45 RPM format and this "O.C. 45" was a short lived experiment until the RCA large spindle hole format became the norm in Canada after 1953. The 78 RPM continued to use the small spindle holes.

45 Capitol F-1067	Nat King Cole	Strange / How (How Do I Go About It ?)
issued with tri-angular optional center by Capitol Records Canada (London) in 1952
45 Capitol F-1246	Frank Sinatra and Billy May	South Of The Border / I Love You
issued with circular optional center by Capitol Records Canada (London) in 1953

One odd question ... which O.C. was better ? .. tri-angular of circular ?

It is also interesting to note that at this time in the 1950s Capitol was using a different set of catalogue numbers than the USA. In the USA these two 45s were issued by Capitol on 45 RPM as F2309 (Nat King Cole) and F2638 (Sinatra/May)respectively.