Ruger makes New Model Blackhawks in two sizes. Large, which includes the Super Blackhawk and Medium which is the same as the Old Model .357's. The 50th Anniv. .357 and some of the recently released "Flattops" are built on the Medium sized receivers.
IIRC, the "protected" rear sight cylinder frame/receiver design, first introduced in late '62/early '63, was originally produced in both sizes but since the introduction of the New Model in 1973 all the "protected sight" cylinder frames are of the Large Size.
The Ruger Vaquero has the same sized receiver as the Large Blackhawks. The New Vaquero utilizes the smaller, Medium sized receiver. The "New Vaqueros" are marked New Vaquero.
Confusing? Of course.
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