Magazine
No such Ruger ever made
Primarily in the magazines; Mark II has a bolt hol open also
Go to Ruger's web site to find out.
Ruger's web site has sn tables.
Ruger's website has extensive sn data. But the Mark III started in 2004, and is still be produced.
Just bought a Ruger Mark II .257 Roberts paid $549.00
Unknown caliber. Contact Ruger
Ruger has sn data on their web site.
Ruger's website has a sn function.
Contact ruger and request a owner's manual
No