I think to sum it up Sandy, the 5 lights in the stamp set were issued as GLOWS, 3 were changed to LE's and renumbered, and 2 remained GLOWS because they had previously been issued as LE's.
GREAT LAKES STAMP SERIES (All 5 are HL 400; all 5 flag numbers are A 682):
Spectacle Reef, Michigan HL 182/410
St. Joseph, Michican HL 183/411
Split Rock, Minnesota HL 124/412
Marblehead, Ohio HL 121/413
30 Mile Point, New York HL 184/414
Thus in your above example, the Split Rock and Marble Head numbers refer to 2 different lights, and the other 3 pairs refer to the same light.
