My old pattern is indeed 15 1/2" for a 40" chest, just like the table.
The new one is 16" for the smallest size, 40" (not 16 1/2" sorry) It was difficult to measure with the overwriting, but it is definitely bigger. I measured button to buttonhole and then overlaid the old piece. After remeasuring many times, my head is spinning, hope it is clear when I come to cut out.
Their own table says, "size is determined by the neck measurement". Then why not put it on??? The pattern is actually is from 40" as the front shows, but the back of the envelope only gives measurements for 42" up.
McCalls do S/M/L etc and give the chest sizes for them, but no neck size. Soon it will all be a moot point, because the men's patterns are disappearing.