Imprint On Tuckaway Barrel

[halfhyde]

I have a Sheaffer Tuckaway with SA imprinted on the barrel underneath the W.A Sheaffer...What does SA mean?

What is says is this:

W.A.SHEAFFER

FORT MADISON, IOWA

SA 600

I get the 600 but the SA?????

I tried to take a picture but the imprint is too faint for my low end camera

Thanks,

Michael Little

Phoenix, AZ