I didn't know what this was when I found it, but thought it was a beautiful tool so scooped it up. Happily, there's a mark on the blade for Miller Brothers, which led to learning it is--and least I think--an antique fleam, a medical tool, which would have been used for making incisions in the skin. (And then just last night I was watching the HBO miniseries about the life of John Adams, and there one was very much like this one, being used to deliver smallpox inoculations to Abigail Adams and her children.) I have, however, also seen some very similar this listed as "ink erasers" and scraping tools--so clearly this could be put to all sorts of creative uses!
19th century or very early 20th century I believe and really in excellent condition, with a beautifully shaped hardwood handle and steel blade. 5 11/16" l x 5/8" w.