I've studied this piece and I think it is old. Do you share the same opinion?
These pictures are insufficient in size/resolution and number. With monochromes glaze and and clay body must be viewed in more detail because other factors like decorations, etc. are missing. Any blemishes or production faults should also be clearly visible.
are these sufficient ?
are these sufficient?
There can be a black(ish) ring on the unglazed ring of the bottom, but it is suspicious that it is all black.
I have doubts about its color, which does not seem right for Longquan ware. The vertical lines are also a bit too many, compared what one usually sees. If the real color is close to the one shown in the bottom picture, I would advise to leave it alone.
Unfortunately, I would need a hands-on inspection with this. BTW, this would be fairly expensive if authentic Longquan ware, but fakes abound.