I got a junk pen for parts today and the nib says Waterman's Emblem Pen instead of Hundred Year Pen. Is that a substitute or replacement nib?

It may be neither. When the FTC upset the warranty cart in 1945, the result at Waterman was that the Hundred Year Pen disappeared and was replaced by the Emblem Pen -- which was identical in every way except that it didn't say HUNDRED YEAR PEN on it. Your pen could be transitional production. Or the nib could be a later repair installation.

Thanks Richard. It does say Hundred Year Pen on the cap, so I guess a very early transition or possibly a later repair.