Noise from watch...

[goduke1]

So just the other day I was commenting (to myself) that my Rolex was silent when it was shaken, and a nice Seiko 5, and my Seiko Kinetic made a noise when shaken. In both the Seiko's it's the rotor turning you can hear.

Well.....I just noticed that my Rolex now has noise when I shake it or shake my wrist. It's not real loud, but you can hear it. It's a high pitched "tick" almost sounds like something hitting the inside of the case or case back. Watch was last serviced in 2004 and is a daily worn watch (not to mention vintage).

First, is this normal and I just didn't notice it before?
and second, what might it be if it's not normal?

Since it's getting close for a service, it might be time.

The serial number was hard to read, but from what I can tell it dates to 1977 5500 model Air King.