Depression Era Tramp Hobo Art Primitive Painting on Metal 1930s Anonymous Artist

Metal circular tray with primitive folk art painting depicting a a birthday cake and birthday message. We have acquired four of these painted trays. They are painted on VERY heavy metal trays. These trays might have been some kind of lid to a cannister of some kind. I am not certain what kind of paint it is, but i think it is oil. Judging from the weight of the metal and the style of the paintings, as well as the themes, i am guessing these are Depression era, or possibly post war. But definitely very old. I am not experienced in evaluating or appraising works like this, so i am beginning the bidding low at $45 to let you expert collectors out there decide what they are worth. This particular piece depicts a birthday cake with a large bird, some mice, another creature, and a person in a hat, along with some pineapples. The painted message reads "Happy Birthday Grandpa Spot 'Granny' El." There is no signature on this piece. It measures 13 inches in diameter. The condition is very good. Please examine photos. Multiple auction winners save on shipping. Thanks for looking.