The action number is 6021
The rifle's serial number (on action and wood) is 21118.
4-digit barrel number is 3618.
Nitro Proved 6.5mm
Underside of barrel shows
s
2
+.1
H
2
1
B

Note that the capital letter B is alone, not near the serial number.

There are also H-within-circle, I-within-circle, crossed banners, crown-over-V, various other assorted digits, and a +2 on the underside of the big ring of the action.

Barrel = .510'' at the muzzle, the lower portion of the magazine walls are reenforced on the outside, and the rifle has the patent sights -- of which the rear striker-mounted peep is missing parts.

Do you have images of a complete Jeffery Patent 8872 peep sight?

--Tinker