Hi RRAdams! That one on the lower right looks like my White Chinese..although the knob on the nose isn't very distinctive yet..(young yet, I would guess) I'm new at this! I love my Chinese, although he can be 'difficult'! Lots of personality!! He and his mate were my first (from Ideal). I lost his mate and replaced with 2 Toulouse..that are sooo different. I didn't know their personalities could be so different! They have so much more personality than chickens! Enjoy!
A purebred Sebastopol would have significantly more frizzled feathers beneath the wings and along the belly. Yet this bird seems to have the typical feathering along the sides and belly, complete with a tuft on top.
While I'm not sure how this happened, I'm going to guess this is a rather splendid looking crossbreed. Especially after noticing what appears to be a Tufted Roman standing to the left of your mystery goose. They don't look all that dissimilar.
Ideal Hatchery includes this description on their website in regard to the "Hatchery Choice Geese" package: "Hatchery Choice Geese is an assortment of all breeds of geese that Ideal hatches which have not been sold as specific breeds of geese. Sexed geese are available as specific breeds, but Hatchery Choice Geese are sold only as Straight Runs (as hatched with males and females mixed)..."
So unless a buyer managed to special order males or females, I would guess there's a good chance that some of these geese (perhaps not all, but some) are mixed breeds that simply couldn't be guaranteed as purebred. But this is just a speculation.