I just purchased a El-Nikkor 135mm off of ebay (actually I just got it!) and it did not come with that little ring to secure it to the lens board. Its the same size as the one that fits on my El-Nikkor 75mm... I gather perhaps its a 39mm, but i'm not 100% sure. If someone could confirm or deny what I need then I would be greatful. Also it will go on my Omega D6, on a triple lens turret.
Also since its easier to post in one thread, if you have an extra you wanna sell let me know, I also need another lens board for that lens to go on(the oval looking one for the lens turret)