Impressed Capital R Pottery Mark - Medium Sized Footed Bowl

Hello

Yet another piece that doesn't speak to me however after some time I found an impressed capital letter on the base.

Very faint under the heavy glaze but at the right angle I'm pretty sure it's a capital single letter R within a rounded surround.

Some 6.5 by 4.5 inches, quite dark brown pottery showing on unglazed base rim and the sgraffito decorative design around the upper bowl.

I could not find the mark and all help is welcome, thanks.