The M1icon carbine was made with mostly parkerized parts, with a couple of blued small parts; the "brown" you describe IS rust, a sign of heavy use &/or neglect. It may also be a re-import from Greece. The rear sight in a bag is a sure sign of abuse by Bubba, possibly irreparable.

If the barrel is bad (worn, rusted, or pitted bore), or it is worn out at the muzzle (measured with a gauge or a round of .30-06 stuck point first in the muzzle), it will cost $350-500 to replace.

Jim gave you the possible high value; a pessimist such as myself would estimate the low side value at $200.

Neal