sounds more descriptive
. Seem to recall that when it's convex (rather than concave like this), the the W/Fs people call it cogged - but knurled sounds just right.
Appreciate this is getting a bit sidetracked, and no objection to moving if people wish, but..............
coming back to the proverbial W or M matter - am attaching pix of the stemmed eye bath showing what does appear to be a W. Doesn't tell us anything about a maker, and may not even be related to the base letter on the Davidson pieces, but thought it worthwhile posting the pix in case of interest.