My 5906 ADJUSTABLE sight must be adjusted almost to the far right. I noticed the Body of the sight is off center to the left. How do I move the sight body? I doubt it is drift adjusable.

Theye are not drift-adjusted. I recently shifted both my 439 and 5904 OEM adjustable sights to the right in order to center them.

The rear sight body (part that has the evevation adj. screw in it) has to be removed to reveal the set screw that secures the sight base to the slide.

1) Push in the (2) plungers that secure the front of the sight base to the sight body, being careful to prevent these spring-loaded parts from flying away. I used two very small flat blade screwdrivers but two awls, two small nails or even toothpicks would work.

Be careful not to allow the spring-loaded plungers to fly away and be lost during htis process!
2) While pressing in the (2) plungers far enough for them to clear the sides of the sight base, gently move the sight body away from the siight base by using a small flat blade screwdriver or similar tool as a "pry bar", placing such tool between the front part of the sight body and sight base.

3) Once you move the depressed plungers up and out of their holes you can remove the body from the base. Watch out for the spring-loaded plungers!

4) Under the now-exposed allen head set screw is a hole in the base that's slightly larger than the screw threads, allowing one to use a non-marring brass, nylon or plastic drift to gently drive the sight in the direction desired.

5) Once you've centered the sight base, tighten the allen head screw to secure the base to the slide. Some might suggest using blue Loctite on threads but I did not.

6) Re-install the sight body by reversing the proceedures in 1).

I'm gald to finally give something back to the forum users.

Thanks ron, that explains a lot. Looks like a good job to be done inside of a clear plastic bag.