1803 Ein Volles Glas Des Gastes Spass

Hello, my name is Michael. This Stein was handed down to me and I was told it was from my grandfather and was given to him by his father. I took this to a dealer who told me that it's very special and unique due to the stamping on the bottom which most of them do not have. He was unsure what it meant or means or what it's even worth. He told me that the date stamp inside of the handle is when it was made. He told me that it's handcrafted, hand painted, and also a unique design. He believes that it is one of kind and there are replicas similar to this but the writing on the bottom is what separates it. He offered $500.00 but hes a collector with a pawn shop which might indicate it could be worth more than $500.00. I'm looking for assistance on knowing more about this piece and if there is a collector market for it. Thank you