Hmm, :hmmm: Neil, you may have just made my day. The description above sounds very like my Charnley Forest stone gotten from a vendor of antique tools in the UK thanks to littlesilverbladefromwale.
It is shown below underneath the Charnley that hi_bud so kindly loaned to me for a comparison. :tu
Edit; hi_bud's stone is a lovely piece as well.