Marked H.D.S or H.O.S '68 glass bowl MOD

I've had this for a number of years now. It's signed but I have no idea who signed it.

there are a lot of people that are very into MOD glass here so I am hoping someone will know. It's extremely heavy. Marked H.D.S or H.O.S '68 clear white and lime. It's cased. Guessing Scandinavian but not sure of that by any means...

I am cleaning out my garage so you'll probably be seeing a lot of things from me that aren't typical from me in the next week or two. :)