Just looked it up on internet...
Yes it is a Japanese ink line (Snap-line) but this one looks like it held charcoal or ash in the pot,
(used for temporary marking cloth, rice paper, etc.) normally it would have ink soaked cotten in the pot.
the line was pulled through, hooked at the end, and laid to mark thin stright lines.
some Japanese Kanji caracters on the wheel, need it translated. (probably the owners name)
6 1/2" long, 2 1/2" wide, 2 1/2" wheel, with stiff silk thread. & white inserts that the thread passes through. (looks like Ivory)
looks very old & hand made.
One man's Junk is another man's treasure