This is a page from the book "Before Threads" by David & Marilyn Delling c. 1971. It shows nine different markings (or absence thereof) for the Brooks paraffin insulator style patented in 1867.

I have been collecting these for almost thirty years and have been successful in identifying only six of the markings. I have never seen or been able to document the existence of markings IH-3-C, IH-3-D, OR IH-3-G.

I would be most interested in verifying if any of these three markings actually exist. Any assistance would be appreciated.

Thanks in advance, Mike