Stelco and the new Mackenzie building, 1960

This the way they used to build skyscrapers, structural steel frames riveted together and if Stelco Steel had their way in the early 1960s- bolted together instead. 
Possibly the collapse of the Union Carbide building on Eglinton Ave while it was under construction two years before opened the door to alternate building methods and material specifications. Coincidently both buildings were designed by the same architect firm, Shore and Moffat. 
Looking at buildings going up these days, the preferred method seems to be a poured reinforced-concrete honeycomb. 
   Toronto's Second Empire styled Post Office (built 1872-74) was torn down to make room for the Mackenzie building which was constructed to accommodate the Canadian Government's need for more office space during its expansion in the Postwar period. Located at 30 Adelaide East it served various agencies for nearly 30 years till it was sold in the late nineties.
 Unlike a lot of buildings of that era it was not torn down and has received a new lease of life as the "State Street Financial Center." I think I still prefer the Post Office building.

The eighth Post Office, 30 Adelaide St. E. 1874-1958, 
Architect Thomas Fuller