Quote Originally Posted by ac12 View Post
The part number on my turret is 404-867.
Is that the thicker turret?
That is the thinner mount turret. The thicker mount turret is the 404-866.

From KHB Photografix:

"Note: Early D-6 enlargers used an early version of the turret (Cat. #404-866) with a thicker mounting flange. The two types of turrets look alike but are not interchangeable. If your enlarger is an early D-6, we can substitute the early turret on request."

Also take a look at this KHB Photografix Omega D5/D6 Lens Mount Reference Chart.