Your Remington model 721 was produced from 1948-1962. If you can supply the 2,or 3 letter code on the barrel we can pinpoint the month and year of production.
check the date code stamped on the barrel. Remington Society of America, Manufactured Date link has the details.
1994
270 is a caliber not a model... For date check the Remington Society of America site for the date barrels codes: http://remingtonsociety.com/rsa/questions/barrelcodes
@ 1954
Proofhouse.com has sn data.
100-450 USD or so
425.00 to 450.00
100-500 USD
100-500 usd
50-500 usd
100-400 USD depending on condition.
your Remington 760 is going for between 200-350 dollars,at this time.