If you put your ear close to it, and move the focus a bit forwards and backwards, I guess you can hear it being a bit "crunchy" or dry as metal grates against metal. It's worth getting re-lubed. My 50s (50/2 Nikkors) are a bit dry so they are going to be sent off soon.

This is a really good place to look for serial numbers and other technical stuff:
http://www.photosynthesis.co.nz/nikon/serialno.html