I've been collecting vintage Rolex for over 10 years now. Many of the Rolex when first bought were either beat up in very bad condition, or simply in parts. The fascination of collecting Rolex is that many of their parts are commonly shared among different models, and thus they can be "transplanted" and bring it back to alive by a professional watchmaker. This applies to parts such as movement, crystal, winding crown, hands, etc. As growing no. of  RSC are no longer servicing vintage Rolex, the future of this hobby will be really relying on those who still have the knowledge and the parts material. Below is a small parts summary of a few popular vintage Rolex :

MODEL                CROWN SIZE            CRYSTAL No.

1. Explorer 1016 -  6mm winding crown  -  Tropic 22 crystal

2. GMT-Master 1675  -  5.30mm winding crown  -  Cyclope 116 crystal

3. Day-Date 1802-6  -  6mm winding crown  -  Cyclope 114 crystal

4. Air-King 5500 - 5.30mm winding crown  -  Tropic 12 crystal

5. Explorer 5504  -  5.30mm winding crown  -  Tropic 21 crystal

6. Submariner 5508  -  6mm winding crown   -  Tropic 16 crystal

7. Submariner 6200/6538/5510  -  8mm winding crown  -  Tropic 17 crystal

8. Submariner 6538A  -  8mm winding crown  -  Tropic 19 crystal

9. Submariner 5512/5513  -  7mm winding crown  -  Tropic 19 crystal

10. Air-King Date 5700/5701  -  6mm winding crown  -  Cyclope 117 crystal

11. Turn-o-graph 6202  -  5.30mm winding crown  -  Tropic 10 crystal

12. Submariner 6204/6205  -  6mm winding crown  -  Tropic 16 crystal

13. Daytona 6234/38/39/40/41/62/63/64/65  -  6mm winding crown  -  Tropic 21 crystal

14. Milgauss 6541/6543  -  6mm winding crown  -  Tropic 20 crystal

15. Sea-Dweller 1665  -  7mm winding crown  -  Tropic 39 crystal

If you have any question on any other Rolex model, please feel free to ask. I will try my best to answer you shortly. Good luck and have fun.