The serial number should be on the movement.

There is a serial number database if you scroll through thread to locate it.

http://xflive.thewatchforum.co.uk/index.php?/topic/50202-dating-vintage-watches/&do=embed

Cheers Martin

 

Serial number is usually under the strap at the 6 o'clock position for most Rolexes. Simply pop out the spring lug and it should be engraved on the case underneath.

Just twigged that P/W probably means pocket watch... which makes that impossible....