Hi Paul,
Your foot type in known as a flanged foot , another type of firing foot , though not specifically a ships firing glass , Ships Glasses usually have exceptionally wide feet for stability in the high seas ,
Single Series twists are those that contain only one type of twist,ie a spiral gauze on its own or a multiple of identical twists , a pair of spiral gauzes or four spiral gauzes, a double series contains 2 types of twist ,ie a corkscrew with 2 threads around it, or a gauze with a multi ply band around it , 2 distinct elements to the twist , and occasionally you will come across a triple twist, once again though thought has moved on from both Haynes and Bickerton so some of the glasses which are described as single series twists in those publications are wrong.
you can see an almost identical dram to mine in Haynes ,plate 90 d ,with green as the colour , but i think more than likely from the same chair as mine .
I had thought of each glass being shown in a new post and if this is preferred I will do that for the next 1 ,if so could the mods change the title of this post to , Ex AC Hubbard etc glasses 1 and 2
Cheers ,
Peter.