I have the revolver over 15 years 8 3/8" brl. The cylinder locking lug isn't in the shape of a T but is off center, most lugs have the T shape. Any reason why mine is off center. Revolver has no problems, it's still tight no endshake.
If your talking about the bolt that extends up from the frame to engage /lock the cylinder notches then it is rounded on top. Never seen a T shaped one.
In the case of the 29/629's made from the late 80's on, the notches are longer than the bolt and not centered.