Royal Crown Derby Vase

We're hoping to get some feedback on the value of this piece.  We purchased it from a garage sale from a woman who knew nothing about it.  Because of the backstamp and after doing some research we know that it is a Royal Crown Derby urn/vase manufactured in 1920.  It was hand-painted by Cuthbert Gresley and was signed by him on the painting and we believe he was the one who printed the words "Brigg of Turk. Scotland" on the bottom since some of the printing seems to match the style of some of the letters in the signature.  It is cobalt blue and gilt.  We believe it may be missing a top piece, but cannot be sure.  There is a very small chip under and inside the rim of the bottom that cannot be seen while displayed and barely seen with inspection.  We are hoping to get some idea of the value and any other information that might be out there.