These things can be quite valuable if they're authentic, so you definitely should have it authenticated and appraised by an expert, I would suggest taking it to your local museum and see what they can tell you. They probably won't give you a valuation of the piece, but they can more than likely tell you something about this jug and it's history, and/or recommend an expert for you.
Re: antique mexican pottery 2222
These things can be quite valuable if they're authentic, so you definitely should have it authenticated and appraised by an expert, I would suggest taking it to your local museum and see what they can tell you. They probably won't give you a valuation of the piece, but they can more than likely tell you something about this jug and it's history, and/or recommend an expert for you.