That's odd - that really looks like Michael Harris' writing, but it's hard to see it properly. I really would not have expected to see him having bothered scribbling on the bottom of a paperweight!
Can you try rubbing some talc over the mark and retaking the pic, Marc?
These are the 2 bits I have with his writing on the bottom. The ink pot has a round polished pontil mark, the inside-out, just a flat polished base. I don't have images of the marks.