Hello again,
This gets curiouser and curiouser. I popped the details from the Family Search results above (thank you again!) into my Ancestry tree and for Herbert John Carnall's "new" American wife, Elizabeth A, a lot of hints popped up. One was a Pension index - attached.
See the reference to an alias Joseph Berker!
I popped the name Joseph Berker into Ancestry and lo and behold, there's a civil war record for a Joseph Berker who was a potter born in England, of pretty much the right age.
The only question I have, the one question that makes me doubt this then is him (though all the signs point to it being him) is in 1868 there is a bankruptcy notice back in the Staffordshire newspapers for Herbert. Does anyone know if he would have had to be physically in Staffordshire to have bankruptcy proceedings? I suppose he could have gone back and forth but from what little I understand of it, passage wasn't cheap.