In 1951 pretty much all D models were Sitka, although some Adirondack spruce has turned up on some. 1953 seems to be the year they started using more Adi for the tops. Given the age, most think there is not much difference in sound. The only modification was switching to Grover Rotomatics in the late '60s. Since I bought it in a pawn shop to play and travel with and not as an investment, it certainly didn't matter to me then. I'm sure my BIL is quite happy with it, too.
On that matter, many who buy as investments often don't play their guitars much. Such a shame, as they were built to make music.