Thanks Peter, I thought it also looked similar to some engraving on two labelled Royal Brierley glasses, albeit the engraving seems pretty crude on the stirrup cup - the back leg of the horse is just, well... weird frankly. I did wonder if the engraver had ever seen a horse before.
I'd come to the conclusion that it is difficult to tell the difference between centuries so it could be 20th, but then wondered if Stevens and Williams would have let that engraving out the door? It's really oddly done I think.
I'm trying to marry it up with the heavy fox head which appears in the S&W book but is not mentioned and I have one as well but mine is not engraved.