Your rifle is a Marlin Mdl 100, made for Sears under the Sear brand name. It was chambered in 22 LR, (and can also use .22 Longs and .22 Shorts) Caliber is generally marked on the barrel. It is prudent to have our rifle checked by a gunsmith before shooting for safety's sake.
Higgins rifle in caliber 22LR will run you about $95 to $150 depends on condition. Check gunbroker.com for more info...
And your question is??
IIRC, a 22lR
10-100 USD
Try the Blue Book of Gun Values.
JC Higgins RifleA JC Higgins model 85 in good to excellent condition with original box is worth about 100 dollars.
Try the Blue Book of Gun Values.
15-125 usd
By a good gunsmith.
Try e-gunparts.com
50-175 usd
Take it to a gunsmith for exact measurement