Thanks for posting this.
The "D" in diamond mark is Dominion Glass Company. Your bottle is mid 20th century.
My hunch is that it is a flavoring bottle. Hard to say much more exactly so your research task is to find a matching example with a label.
Try looking through bottles on eBay with a search like this: https://www.ebay.com/sch/i.html?_from=R40&_nkw=vintage+flavoring+bottle&_sacat=0&_pgn=1
It is old-fashioned detective work - dig, dig, dig and hope for a match!
Good luck and let us know what you find.