I believe the two listed in the 1950 ORD 9 are both early round back type. One each for Spartan & Autolite.

Early Horn has rounded back.

Early Horn has rounded back.
ORD # 7351412, WO # 802893, Sparton # D2140A
ORD # 7728341. WO # 802893, AL # HX4004UT, Sparton # D2140A

Late horn has flat back

Late Horn
Edited to answer questions on indexing

Due to the early horn's dombed rear case the terminals angle outward and rearward. The late horn's flat back case points the terminals straight outward causing them to protrude further out than the early horn forcing the opposite indexing.