Hi, and welcome to the board. Interesting piece. It wouldn't be surprising if it turned out to be quite old, with the machine threading to the rim. I couldn't find anything in Gulliver with the air twist stem, but maybe someone can help. It might help if you could take a picture of underside of the base.
About values, these are so subjective, particularly on eBay, that people on this board tend to avoid giving an opinion.