Unknown line. The Morgantown Glass book, by Snyder, shows them on page 149 and lists them as #7654 cocktails. The stem is the same as on #7654 but not the bowl.
Snyde'sr Morgantown book also mentions that this is a H.I.O. cocktail. Fellow board Member Dick Ladd remembers the followng about this candlestick/stem: " Snyder uses the term H.I.O. on page 149. That means Hole in One and was thought to be a place for an olive to go if the glass contained a Martini.
Jerry Gallagher talked about the H.I.O. in his newsletters but I don't see that it ever made it to his book. I don't have the newletters any longer since I am not as active in Morgantown."