Mike, i looked at both the 1958 and 1959 A2s in their respective catalogs and didn't see much difference except that the 1958 lacing at the crotch seemed to extend a 1/2 inch from the web. The '59 looked flush to the crotch. The 1960 had X lacing all across the fingers which the 58 and 59 didn't.
Hope this helps.
Mike I was working off illustrations and not actual photos also at a back look where there seemed to be separation from the crotch to the web.
But that's my best guess.