GMT 1675 movement questions

[jogren]

Further to my "Newbie" post of 6 October: (I'm too new to this forum to figure out how to insert that link here!) a couple questions:

1) Can a GMT 1675, serial 621550 (meaning it was made in 1960) have a 1560 movement as reported to me by the last guy servicing it? All the caliber charts I have seen here and elsewhere show that this watch should have a 1565 movement.

2) Regarding my question about the number 5/27506 in the movement box on my COSC certificate, one article I read somewhere says this is the serial number of the tested movement itself. Is this correct? I haven't found such a serial number on any of the movement pictures I've seen here so far. Guess this would show that Rolex put in the ref and serial number of the watch above the movement box when the movement was returned to them after testing. Certificate is found among all the other pictures at http://www.flickr.com/photos/ogflick...7627817368646/

Thanks for all your help! Pat