It is unfortunate that there is no background information to this photograph so all we are left with is what has been captured in the image.
1.
Bridge Classification Marking: I did a little digging through my sources and found that the manual Vehicle Markings Canada, 1947 lists several Sherman types including the "
Sherman IV (up armd)" as 38. B-GL-303-008/SS-001 Staff Manuals, Volume 8, Marking of Field Force Vehicles and Guns, Change 1, 1981 lists the "
Sherman Tank M4A2" as 36. So the '38' bridge classification found on the subject photograph is certainly within the parameters of the vehicle as prescribed by DND.
2.
Location of Bridge Classification Marking: We don't have a complete frontal photograph of the vehicle in question, so there may well have been a bridge marking painted on the front. However, attached are three images from my archive taken in 1982 that show the bridge classification marking located on the right side of various vehicles. I did not take the time to dig deeper to see if I have anything from the 1970s, but the location of the marking does again appear to conform to DND practices at the time.
3.
CFR Number: The CFR Number
45-78961 does conform to the CFR convention with 45 representing the vehicle year of manufacture and the five digits representing the number assigned to the specific vehicle on that year. These late war Shermans were originally destined for Russia and instead were purchased by Canada, which again supports 45 being used for the CFR number. Also 78-961 did represent a M4A2E8 Sherman that, according to the Arms and Armour site "https://canadianarmsandarmour.ca/", was in Sept 1962 assigned to the Central Command Pool and May 1965 was in the Central Ontario Pool, which may explain why this vehicle was photographed at Downsview as that was the location of 25 Supply Depot.
4.
Turret Marking: The triangle turret marking, which indicated 'A Squadron' also conforms with the 1947 vehicle marking guidelines.
5.
AFV Crew Helmet: The person in the turret is wearing what appears to be a U.S. M1938 AFV Helmet with U.S. Goggles. While the M1938 AFV Helmets do not appear to have been used by Canada in the post-war era (I don't see them listed in any of the supply catalogues I own), and if this photograph was taken at 25 Supply Depot in Downsview then there is the possibility that there may well have been a examples of this helmet type still languishing in stores that one was brought out for the photograph. Likewise the goggles are definitely U.S. manufacture and these were being used by Canada, the only thing I cannot tell from the photograph is if they were wartime or post-war manufacture.
Rob made a good point about DND policy and how it was interpreted which would certainly explain the markings. The contents/subject of this photograph just shows that knowing the context would certainly explain the anomalies in this image.