As mentioned,, that's a fairly rare version of the original FT .44 magnums. But Ruger may have misinformed you on the date. (Unless you are getting the letter,, they can make mistakes.) #21254 was made in 1959 according to our collector guide, the Red Eagle News Exchange Reference Guide.
And only about 1500 of the models known as "BKH-40" were built.
And those grips are not factory. All factory stags had medallions in them.
If you get the $10 factory letter,, it will give you the month & year of shipping, (unless it happens to be part of the group of papers damaged in a flood,) the correct model (BKH-40 most likely) and even the place it was shipped to.
Even in it's rough condition,, those are desirable guns to many of us. And if you decide to try & get a set of factory grips for it,, you want to original "XR3" grips. The newer XR3 grips will be slightly "off" in the location of the hole known as the grip locator pin hole.