An update which hopefully adds some more to this... I found a clear Sowerby bowl to compare with the pink one at the top of this thread.
The bases are identical in size and pattern when placed over each other. The number of ribs / rays is identical, and the pink bowl looks as if it was made from the same mold as the clear one, but then stretched as I suggested earlier.
I weighed them both on my new snazzy electronic scales and the clear one weighs 1063 g and the pink one weighs 1082 g.
I have side-by-side pics to show the similarities here (click thumbnails to open full size pics):
Bases side by side:
From the top:
From the side: