Ahh, I see a reference that corrects my misimpression .. I don't know why the State department had both FS-240 and FS-545, or how or why they chose between them.
From the time of introduction of the original FS-240 in 1919 ...http://www.state.gov/documents/organization/86801.pdf
No big deal. Both forms are the end result of having a citizenship claim adjudicated.