It all depends on which Ruger .44 mag you are talking about. A new Super Blackhawk is in the $500-550 range depending on where it is purchased, local taxes and accessories. Used models would be worth less, until they get old enough to be in the classic or collectible range. Many people are willing to pay more for the old model 3-screw or Flattop models claiming they prefer the style, however; many view them as "used" and worth less. It all depends on the variables in question.
Ruger's web site has extensive sn data.
$600 USD
100-1000 USD and up depending on specifics
The Ruger website, under customer service, historical data, has date of manufacture data. You can also email them or call them.
No, it cannot.
450 is a normal price in good shape
100-1000 USD depending on EXACTLY what you have, condition, box, papers, accessories, history
Ruger's web site has sn data.
1970
About $400
100-500 or so
No such Ruger exists. What you might have is a Ruger Super BlackHawk. 100-1000 USD or so depending on EXACT confgurationa, age, condidtion.