I have discovered that antique dealers become too diverse in that they do not specialize in one item. There has not been a shop that I cannot find many sleepers. I would suggest staying out of the main stream of collectors of paintings and concentrate on dealers who coup de grass is furniture, glassware, paper, etc. They will stumble upon paintings within their purchases that they haven't a clue about the artist or the works. Mainly because they have purchased their favorites and the painting just was part of the lot.
Go to shops, flea markets, antique sales, thrift shops, and yard sales. These things pop up periodically everywhere. What you have to do is have as much knowledge as possible in your search. You'll be surprised at how much you can find. Sometimes the items appear a bit pricey but set your limits. Take a magnifying glass with you at all times and even a small portable black light to see if you can catch the "repaired" damages.
This is not easy but, in time, you will be able to spot a winner from across a mile flea market. Oh, and a last thing Mohammed, never tip your hand and offer any information on your expertise because you will find the prices go up with each repeated visit and you will have a familiar face.
Just by constantly going to the above places will inspire the dealers to please you and they will also become buyers for you. Sometimes they get grandiose thoughts and raise prices without having any idea what they've got just because they know you buy them. Knowledge, knowledge, knowledge and set those buying limits.
I can only tell you that books are about the best way to learn. There are so many fields in this hobby and it takes years to know what each item is and it's value and you still have to look items up as to their current value. My hobby, coin operated games, has be buying tons of books to stay current with value and new information. I could only guess as to how much money I spend on research books and price guides. As to how to make money while learning, I could only say to try to make friends with someone near you that is into items that you are interested in.
The Internet has tons of sites on just antique slot machines, some with information about them; the library has some books on this also. There are also shows around the world dealing in just my hobby; two shows a year in Chicago, one in California and other places.
Most of the pewter supplied to Marshall Fields came from Richard Mundey, a major pewter dealer in London in the middle of the 20th century. The labels you have will probably be typed on brown luggage tags, using a combination of red and black ink, and some underlining - I know this because they are the product of Mundey's own typewriter!
Mundey was notorious for over-egging his descriptions, using over-romantic associations, and, much worse, he was implicated in purveying pieces dishonestly. In particular, he seems frequently to have 'enhanced' pieces (or had them enhanced), for instance by adding extra marks that suggest an earlier date.
I recently inspected a substantial collection of similar pieces in Massachusetts, bought from a New York dept store I believe - the majority had been messed about with in some way, though a few were good, authentic, original, untouched and desirable examples of British pewter. But there is an important lesson here: having a label purporting to guarantee the authenticity of a piece means little - the only way to establish authenticity is with the help of an honest expert.
The 'ship bowls' may or may not have come from the same source, but I can say with confidence that they are fake. These are very common, having been made as plain bowls in the early 20th century.
You could try eBay, but you will face the problem of needing to know which pieces are 'good', and which have been messed about with. And eBay prices for pewter are not great. No auctioneers in your part of the World will be able to help - they know nothing about pewter - and major auction houses are generally no better. Within the US, New England is the main area where pewter collectors are to be found, but the market for good British pieces is also strong in the UK, where there is a considerable shortage of collectible pewter.