Last I heard the consensus was that pewter bolsters were probably not PC for the 18th century. Don't know if that has changed.
I only know of a handful of examples that I feel reasonably certain are 18th century, and none have pewter bolsters. With maybe two exceptions all are very crude, BTW. Of the two exceptions one has a solid pewter handle with a lion's head grip, and the other has a iron ferrule.
I think that there might be some 19th century examples with cast bolsters, though.