The only real differences Ive been able to see are the plate like armour locate under the belly, (shovelnose) and that the sterlet is supposed to have a more pronounced white trim around the fins & tail.
There may be more, but thats all I know.
Mine does indeed have two separate plates under the belly, and the fins don't have white trim. The edjes are a little lighter gray, but I think thats because they are so thin there that light makes them look lighter.
