Janice I'm with you & am not 100% convinced this is USG because of #1 the bottom & #2 the flaired top. The 15179 simply does not exhibit this type of flair, its flaired yes, but not to this extent. There is however a problem totally discounting the possibility...the USG Aurora stretch line was initiated in October 1921 primarily in Factories G & R & continued through 1926. These were early forerunners for later 151 line pieces & I was informed years ago that molds were changed out & some early molds were discarded/modified during the production of Carrara which was a heavier (weight)opaque & did not work well pressing Carrara. If you ever (and I know you have) picked up a piece of 151 Carrara & compared it to a piece of "normal" 151 there is a substantial weight difference so I'm wondering if the possibility exists that this was an earlier mold that was later discarded when Carrara production began. Thats the only possibility I can think of regarding saying this is for certain USG. To me this is a tough piece to attribute 100% as being USG unless its a modified mold. Ken