First you should try oiling it with some non detergent 10w30 oil it might stop the leaks. As far as repairing it call Tim at mac1airguns, you can either have him rebuild it or order the parts and do it yourself. Also if the breech is flat on top with grooves in it then it should be mid 70's or earlier.
20 cal, the round was created first then a gun to shoot it ) does it have a hold down safety or a rocker safety ? it should say c-series-made in USA on it, but either way it's a c series, originally the blue and silver streak were a different series, but eventually both became c series guns ( because the finish had become the only difference between the guns, as apposed to the silver streak having a slimmer stock than the blue streak ). Look just forward of the breech and a little low on the receiver on the left side and there should be a serial number.
