I have a Masters, but it was in Museum Studies, not dating jugs - inded, you will find that Masters fall into two kinds: subject-specific, be it paintings, Roman archaeology, Zoology, or whatever, and museum-specific. The first kind gets you an expert in paintings (etc.), the second kind an expert in everything from how to write an acquisition policy to how to dispose of collections, via how to run visitor surveys.
OK, this is how I'd do it if it landed on my desk. First, I'd look at it. What is it made of? Earthenware? Porcelain? Glass? Plastic? What is it's shape (earlier shapes are copied later, but rarely, 'just right'
? Then I make a guess. This is based on 'where I see it' - does it 'look right' in a 1930s house, a 1900s house, an 1850s house? (Am I entirely off track thinking of houses - is this the kind of jug used in hospitals, or in churches?) Then, _starting_ from that hunch, I go and look in books, especially suppliers catalogues.
Another question I'd ask: who is telling me that this is 150 years, old, and does it matter?
For example, someone in their 60s comes in, and says 'this belonged to my grandmother. She says it belonged to her grandmother, who was born in 1840 - so it must be 150 years old. Of course, that great-great grandmother could have bought it in 1900 or so ... but that isn't why this object fits the collection policy - why it fits is because the donor says that he remembers this jug in his grandmother's house in the 1940s. So I'd be more interested in getting a photo which shows how his grandmother used or displayed the jug, than in pinning down the date of manufacture.
I hope that helps,
