How rare is a 68 GSS?

The GTS 383 (GSS 440) were not pulled from the line on December 7th, 1967, but on December 10th, 1967.

I think that November 19th, 1967 is correct, as the third GTS 383 (GSS 440) is dated November 20th, 1967.

Maybe someone else has more details...