I found a Ball Official RR Standard silver tone open face pocket watch at a thrift store recently and I'm having trouble dating it. It has a plastic/celluloid crystal, is 19 jewel and I think 16s. Serial number is B0505673. The back has an engraving of a train that is badly worn. From the little research I've done it appears to possibly be late 1800s? But the serial numbers I've seen don't start until the B060000s. I would appreciate any help that I can receive.
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