I believe your rifle is a Marlin Model 80 made for Sears.
103 is the Sears vendor code fo Marlin firearms
Proofhouse.com has a store brand chart. When you find out who made it a value can be estimated.
EBay for 38.00
Up to $100.
$175-$225.
it is a marlin model 81. good rifle. hang on to it. thanks
Try e-gunparts.com
100-300 USD
No sn data available.
50-200 US Dollars
In the 50s and 60s. You're welcome.
50-150 usd