[3and2]

I've been curious of this Spring Training item I purchased from one of the major auction houses a few years ago. It was listed 50's Yankees team signed w/ a psa auction loa. Anyway, after researching each player who signed the stationary I noticed all of them played for the Yankees in '56 & '57 except for Maurice "Mickey" McDermott who was traded to the Yankees on 2/08/56 and traded away on 2/19/57. Does anyone know when spring training starting back then? Obviously, I would prefer this to be a '56 Mantle signature. If spring training started in Feb. perhaps Maurice signed this before he was traded in '57. Any thoughts would be appreciated. Thanks.