I can't make IOW out of it... lolo or holo... perhaps?
St John's crystal had a copyright thing for making maximals and minimals with Isle of Wight Studio Glass, but things went a bit sour between them and MH and the quality of the stuff they made deteriorated (there has been a plethora of inferior minimal-ly things appearing at various times on eby, en masse - I have presumed somebody bought up old stock from St John's).
The stopper is not right for IoWSG, but I suppose it could be something made at St. John's, either before or after the fall out, or if it does read IOW, it could still refer to one of the other makers on the IoW - Alum Bay or Glory Art Glass?