I am thinking of adding another non-AI-capable body (I have two F3s), and am considering an F2 with a drive. The MD-1 is expensive and hard to find in better condition. The MD-2 can be found in EX or better grade, but I understand it has a plastic gear that tends to wear. The MD-3 is more readily available than either, but Stephen Gandy, in his comments on F2 gear, seems to think it to be too plasticky. In the pictures I have seen of it, it does not seem to be that plasticky, especially in comparison to contemporary gear. However, I have never held or used an MD-3. I welcome any comments.