As far as I know (note the qualifier) the Colt Border Patrol that was actually just the Trooper Mark III, did NOT have a satin nickel or Coltguard electroless nickel finish.
The original finish was bright nickel.
There were 1,152 made in bright nickel from 1970 to 1975. This is before Coltguard was available.
True, I've only seen probably two nickel Border Patrol revolvers but both had mirror polish bright nickel, "possibly" not as well polished as standard Colt bright nickel, but no where near a satin finish.
Both had standard square butt Colt walnut grips, not rubber.
I would suggest being very careful about this particular gun, it doesn't look "right". Possibly it's been rebarreled, refinished, or it's an unknown variation. Only a Colt Archive letter will tell you for sure.