Right they have now loaded. Well done. And (drumroll) it’s part of an EPNS teaset So go on Ebay for a price and half it and you get value. What happened to the rest of the set, divvied up among the grandkids?
May I ask what you want to clean it for? Your own use or to sell? And if to sell to whom? Because if it is Americans they like their antiques grubby. They call it authentic.
Why do you think it is a teapot? It might be a hot water jug which the Americans call a coffee pot.
This page tells you you about the company that made it and you can probably deduce when:
Failing that Bart has already answered the question on another JDS EPNS pot on this site which I presume might be of interest to you:
Happy to do it all again for you, but you should have some fun too!
CRWW