Ah ha. THis grip comparison does not tell us for sure. The one on the left is a Square butt so the grips will be larger -- but I think the length of a RB and SB "regular" j frame is the same.
However, look a the trigger guards -- the size difference becomes more obvious.
I've never seen a small frame Cheif without the grips, but that lower "hole" in the grip frame is more rounded than a typical J-frame.
Yep "Baby Chief"
Even with the re-nickel it is a desirable piece. If it was me I'd swap out the Trigger and Hammer for a case hardened one, just to make it look "right" Finding some I frame grips for it will be a pain, but you could use J frame "banana" grips on it, or get some newer (so not rare) J frame wood grips and file/sand them down. Every once in a while you can find some of these on ebay that have been operated on like this.