Hi Gary
I can't  tell you what it is but I bought one almost like it about 15 years ago chambered for 219 zipper improved. My action exterior is almost identical to yours except it has a swinging lever safety on the right side to block the striker as it is striker fired instead of a hammer fired, top of receiver has a tapped hole down into the bbl shank area and 2 grooves under a claw mount base. Proof Marks are 
R
U
N
With crowns over each letter, located top right hand edge of action and going back, and centered on top of breach block going back, have to hold rifle vertical to read.
This action has a Very fast lock time, less than 1/4" striker fall.
I rebarrelled it to 38-55 for my 12 year old daughter to bpcr
but I never used bp , she's probably shot 3000 rounds through it with no problems other than a poor stock attachment system

RUN  - proof marks
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