Hi all. I recently acquired this Tudor Oyster from a thrift store. I am trying to figure out the date of the watch. I did find a listing here https://sweepinghand.co.uk/useful-info/tudor-serial-numbers/ saying the serial number should be engraved on the case between the lugs. My watch doesn't have that but appears to be on the case back. Anyone have any insight? Is the number on the back the serial number? Thanks in advance.