If your tag and receipt says it's a 2016 model, but you actually received a 2014 model, there might be a case for being able to return the item for a full refund due to misrepresentation at the time of sale. Check your local and national laws pertaining to disclosure and return options if the item is not as originally described.
You said you bought it at your LBS. Chances are your LBS is a Brompton dealer, because otherwise they would not be licensed to sell used or new Brommies. I'd start with the LBS. Tell the owner your concerns about misrepresentation and ask for a refund. Seriously.
If you get pushback on that, go straight to Brompton corporate. They don't want their dealers involved in misrepresented sales.
Let us know how it plays out if at all possible. I'd like to know how the LBS will explain this one.