Sorry, no idea about websites off hand, there were two variations in this design, this one and a narrower version.
Page 78 Millers 20th Century Glass by Andy McConnell shows them and gives a date of "1960s".
Page 156 Scandinavian Glass Smoke & Ice by Leslie Pina and Lorenzo Vigier also shows them and gives a date of "likely in the 1960s".
In my experience they don't seem to crop up all that often, I think they feel comfortable to hold and would like more of them.

The trouble is I have a shelf full of odd glasses, I bet nearly every member of the GMB has too, if not more.

John