Ruger never made the .357 you are speaking of in a convertible with 5-1/2" barrel, engraved cylinder and Bisley grip frame.
But Timbo22 is correct that Ruger is making a .357 Blackhawk in stainless with 4-5/8" and 5-1/2" barrels for Williams Shooters Supply, with several hundred of each having been produced. These two models are convertibles
Chet15