This is a Weigand no drill, no tap base unique to the .480 and .454 SBHs with a 6 1/2-inch barrel.





Here's Weigand's shor no drill, no tap base mounting a small reflexive red dot on a Blackhawk.



Max Prasac

Semper Fidelis

BIG IRON: https://www.youtube.com/watch?v=L6aXjMH5C30

Gun Digest TV's Modern Shooter: https://www.youtube.com/watch?v=nGo-KMpXPpA&t=7s