So as I understand the history, the Dukes County Historical Society was created in 1923 (as seen on the mug) and then renamed the Martha's Vineyard Historical Society in 1996. Now the collection is at the MV Museum. Luckily I have a mug from each of the generations of this great resource.
Here is an article on the history of the history group:
https://vineyardgazette.com/news/1996/09/17/historical-society-gets-new-name
