What is the "most useful guide to the meaning of the words 'fair market value' in the Dominion Succession Duty Act"?

He then refers to the "most useful guide to the meaning of the words 'fair market value'" in the DominionSuccession Duty Act contained in the judgment of Mignault J. in Untermyer Estate v. Attorney General for British Columbia, 1928 CanLII 43 (SCC), [1929] S.C.R. 84, where he said at page 91: We were favoured by counsel with several suggested definitions of the words "fair market value". The dominant word here is evidently "value", in determining which the price that can be secured on the market -- if there be a market for the property (and there is a market for shares listed on the stock exchange) -- is the best guide.