I've recently had the opportunity to study a batch of letters received by a steam car guy in the early '40s. A couple were from Fred Marriott, and in one he mentioned a pricker that he had patented. Here's the patent -

[pdfpiw.uspto.gov]

In 1941 he still had the parts to build several hundred of these, in two versions, pre-1918 and post-1917. I suppose the alignment pieces differed in conformance to the pointed jets vs. the dished ones.

Anybody ever seen one?

I have seen ones like that, surely not originals i would guess. I think Tom Ackermann had been using one when I was learning Stanleys...