rolex and tudor production by serial numbers

[Sidwin]

i have two tudor. one is the 69 sub and one i have no idea. if i take the band off and look at the serial number of the other one my friend left to me when he died, can i figure out when it was made? i want to send it off to mark to to have the band repair. it has sat in my buddy desk and then my desk for the past 20 years. i checked the time on it and amazing it is only off by 20 sec. I was cleaning out my buddy's room and ran across this watch. his dad put it on my wrist and told me to keep it. the face is a little small that what i normally wear but i love how it has all those rolex components like the band, case back and crown.

any insight on what i got would be great.