12p Black 70 years ago

Imagine buying a fine used 12p Black with a Royal certificate for just over $1400?

I came across an ad by H.R. Harmer in the November 1952, Maple Leaves Journal (by the Canadian Philatelic Society of Great Britain) advertising exactly this for £425.

Curiosity got the better of me so I looked up the exchange rate in 1952 and it seems that a British £ was worth about $3.37 CAD. The $USD at that time was worth $1.53 $CAD.

This is only one of many interesting finds in my lot # 2112004 which is a two part, hardbound, set of Maple Leaves Journals from  1947-1959.