We used to make things in this country #301 Canadian Seating Co.

From an old magazine I found, in 1960 this company supplied 3211 York chairs to the new O'Keefe center in Toronto. The chairs did not survive the 2010 renovation, and the new number of seats is now given as 3,191, supplier unknown. 
The company has completely disappeared, I could find no information online and at the address is now a Chinese trading company.

Toronto Public Library

The seats appearing in this photo of a union meeting held at the O'keefe Center in 1968.