100-1000 USD depending on specifics
Ruger's web site has extensive sn data.
If you are referring to the 33 round double stack magazine - I know it will fit the Ruger P-89. If the P-89 mag fits the P-85 your answer is YES.
About $400
100-500 or so
100-1000 USD
The Ruger website, under customer service, historical data, has date of manufacture data. You can also email them or call them.
50-400 USD or so
100-1000 or more depending on specifics
75-225 USD
10 bucks
100-1000 depending on specifics