I would say 1967-68 was the very first timeline for the stiff synthetic ones.

There was perhaps 5 years of overlap, in which felt, cloth and synthetic were all used. Felt and cloth pennants steadily diminished over this span, and following 1973, the only pennants being made were cheap synthetic garbage.

Hank, this is a recent pickup of mine, this sheds some light on things I think. (I guess you may have seen pics elsewhere, I’ve never seen the 1960 phantom version before.)

Thanks, Greg. Great pennant, I think I remember that Rob has a 1960 version like that. Not sure that helps date mine, though, as that image could have been recycled from an earlier pennant. It is informative that pennant artists liked to use earlier uniforms because of the absence of a face mask, that makes all kinds of sense and pretty much eliminates the possibility of dating football pennants by the equipment pictured on the pennant, which is much more likely with baseball pennants, it would seem.