The XTR on your rifle was to indicate the level of finish to it.Some say it was abbreviated for Extra.
With the serial number that you have supplied,your Winchester model 70 rifle was made in the year 1979.
500 USD
Your Winchester model 70 XTR sporter was produced in the year 1988.I am in the process of buying one that is new in the box also.Mine is chambered for the .270 Weatherby Magnum,and was made in the year 1988.
Your rifle dates from the year 1987,with the serial number that you have provided.The XTR series was discontinued in the year 1989.
Depending on condition anywhere from $350 to $500.
1992-1993,for the serial number provided.
Try Proofhouse.com
I have one I purchased new in 86 serial 1825328
1992-1993,with the serial number provided.
0-1500 USD depending on exact configuration, age and condition.
I have a Winchester model 70 that I purchased new in 1979. It's serial # is 1,430,611. Yours was probably produced 3-4 years later.