need a bit more info , like just which caliber Blackhawk are you referring to???
the larger, bigger framed Super Blackhawks came out in 1959, lotsa details can be found in the various Ruger books written over the years by many collectors, and a picture says "a thousand words"......
If your Blackhawk, serial number 238 is a .44 magnum,, it'd be a "Flattop" version. Made in 1956 likely.
The Super Blackhawk came out in 1959, larger mainframe, and a Dragoon trigger guard. There are other differences,, but that's a few that are easy to spot.