Sorry, coming in a little late on this one, but when you say 'sans serif' font, are you referring to block-type lettering on weapons vs cursive style? If so, there are multitudes of examples from the late-18th with said font. If I am mis-interpreting the question, please ignore my comments.
Specifically, early (ca 1805) swords with block letter "GR", the markings of Wooley swords, Dawes swords circa 1790-1800 period.
