I'd like to get a follow focus for the Canon 11.5 - 138 S16 lens that I use with my SR3, however I see that there are a few different standards for gear sizes (MOD 0.8, MOD 0.6, and so on), and that even within these standards, there are various tooth counts (MOD 0.8 w/ 35 tooth count, MOD 0.8 w/ 42 tooth count, etc.). Is there any way for me to figure out which "MOD" standard and tooth count would be compatible with my lens? I'm not sure if the gear rings on my lens are factory originals, or if they were added by the original owner (my lens was originally a rental which I purchased from Otto Nemenz).
I've included a photo of my lens for reference. From the photo, would anyone be able to make an educated guess as to which follow focus gear I would need for the lens?
Thanks to anyone who might be able to help!