having now looked at TNA pix for 189121/2, there are notable design similarities with 183352/3, but I'm no wiser unfortunately, as to why the factory drawings for the earlier pair, together with Jenny Thompson's drawing, show those large stars, and your creamer doesn't (neither do stars appear on 189121/2). This doesn't mean your piece is unrelated and it has such a close similarity in other respects, but I'm no expert on this factory - perhaps Neil can give an opinion

Jenny Thompson was obviously keen to point out in her book that the sugar and creamer were adorned with "large star pattern grouped round middle", for 183352/3.
Drawings for both 189121/2 show a lidded butter dish with an impressed star to the base, and a raised cogwheel pattern in relief around the rims of both the base and lid, and on the finial of the butter lid - but as I say no stars. This cogwheel pattern is common to all four Registrations - the earlier pair date to January of 1865, and the later pair to August of the same year.
The earlier pair of Registrations are for a sugar and creamer, and my opinion is that the later pair of Regs. refer the lid and base, separately, of the butter dish only.
Will post pix shortly - am still mystified as the absence of stars on your creamer, assuming it is related to Reg. 183353.