From Linebaugh's Custom Sixguns;

"FRAME STRENGTH

Here at Linebaugh Custom Sixguns we build some of the most powerful handguns in the world. All of our guns at this time are built exclusively on the Ruger Blackhawk frames. (Ruger Super Blackhawk, Blackhawk and Bisley models are all identical. All frames in the new model that was introduced in 1973 are the same.)"