We've quite recently had this information on the Board, including Glen's original and very interesting research data, which can be found here...http://www.glassmessages.com/index.php/topic,48998.msg276260.html#msg276260
...... provide you have the stamina to read through the other bits and bobs.
Incidentally, the height is c. 10.5" (270mm).
However, I feel deprived - my own example of this decanter is without a Regd. No...........although it does carry the words JACOBEAN REGD in relief down at the very foot, so there is no doubt as to it's provenance. Fred doesn't mention these trade mark words, so presumably the pair being shown here don't have them.
For very obvious reasons, these aren't pressed in the sense that a plunger has been used, and although I don't know for certain, I'd suggest that they are mould blown, pneumatically, but I'd agree that the stoppers, being solid, would be pressed.
It would be interesting to know whether Natalie's pieces (can I say that) have the mirrored bases, or not.