Kearney
The originol 36x did not have a locking objective.
The 36BR is essentially the same scope, but Leupold made an entirely new front lens assy to encorporate a locking feature. I believe the erector tube and other internals are the same. The actula glass objective lens its self might be the same as well.
On the BR-D, Leupold did away with the small "arch spring" that held the erector tube against the adjusting knob abutments, and went with a more massive forked style spring. They also had to reduce the diameter of the erector tube to get it all in there. There are a few other things that they did to accomadate this, but all in all, it's the same scope.
All of these are excellent scopes, many still believe this was Leupolds best design and wish they had not quit making them. The addition of a Tucker Conversion will shore up the only suspect part of these scopes by stabilizing the erector tube in thge radial plain where it pivots at the eye piece end. But I am not sure about this voiding Leupolds lifetime warranty. Through the years, their policy has changed......jackie