I've been sitting on the sidelines on this topic. I would suggest that the OP visit
http://cardersteubenclub.org/ for further information. I have over the years sold seven pieces of Alabaster/Jade & Alabaster/Rosaline & in each case they carried the Steuben’s pre1932 acid stamped mark consisting of a fleur-de-lis with the word Steuben within a banner as do the vast majority of pre-1932 Steuben art glass pieces. Also with the exception of very high domed footed pieces the vast majority of pieces have highly polished pontils. Exceptions though exist, especially stemware.
Then there is this. In the mid 1980's an import firm from the U.S. (whom obviously I will not name) imported Steuben Alabaster & opaque combos from Italy...Seguso was suspected as the manufacturer, but as far as I know never proven. These pieces were good & I mean good copies in both design & color, however two issues were spotted, #1 they carried a block Steuben signature not particularly well done, none carried the fleur-de-lis signature & #2 the Alabaster was too white & too translucent. I remember it caused a stir to say the least in the market & this was pre-modern WWW so word was slow to spread, you have to be old enough to remember sometimes to remember these things.
I'll close by saying that the OP should seek out professional assistance from someone specializing in Steuben or ask the experienced individuals from the Carder Steuben Club regarding this issue, especially since none of us here can actually hold the piece in our hands from close examination. My opinion only.
Edited: This is the groups URL for Steuben signatures, both legit & not so legit.
http://www.cardersteubenclub.com/aboutus/about-view.cfm?category=Signatures