The collection is arranged in two series; Series 1 contains the Schirmer materials, and Series 2 contains the Galaxy items. They are numbered within their respective series, so that the numbering restarts at "1" in Series 2.

From SMU's Guide to the Ferde Grofé Collection:

Galaxy — These items were extant in the gift and the card file.

Schirmer — The same holds true for the Schirmer as it does for the Galaxy items.  Inventory was taken, but no conservational tasks were performed.  Also, like Galaxy, the Schirmer items are all published materials from Grofé’s working library and were not written or arranged by him.

Grofé, Ferde (1892-1972)