One word of caution about the 1925 Exhibits Gehrig is that it is often mislabeled by the TPG's with the 1926 version which looks exactly the same, but has a bluish tint. For example, here is one that sold on ebay
Link, that looks like it is a mislabeled 1926 version due to the bluish tint. Of course, the 1926 Exhibits is actually rarer than the 1925 one.