Dalmore Yellow hone

[JM1975]

Hey all,
Im new to this forum and mostly seek advice and value indication on a honing stone i came by on a flea market the other day... it came in a box of some tools that had little value except this stone and a few chisels
My first impression is that this has never been used before I bougth it. Any thoughts on what its worth or if its a rare collectible item or such..?