As Sach says, this is definitely a cut-off. Most likely from a paperweight but it could be the cut of from a blown piece. It could have been made by a master or a student, but as a by product, this is really irrelevant as you would need the actual piece to know.
One of the fascinating things about the glassblowing process is that you create what are effectively glass "tools" that are used for a purpose on the journey towards the finished piece. These are usually discarded. Some people save them and use them as inclusions in other pieces.
Just think...there would have been one of these for every crown weight produced! But most of these will have ended up in the bin. Some people might say that makes them rare....a whole collecting area that has been overlooked.