Penny red, single watermark.
V/10, at right, has a sloping (sometimes notched) top right corner of the crown cross and a curved compartment line outside the NE corner. V/9 often has a thin white flaw where the shading joins the SE corner of the right value shield (only a hint of it here) and can have a small compartment dot outside the NE corner (present here).
If planning to buy more than one item from me, please use “Add to Cart” not “Buy it Now” or you won’t be able to combine postage.