Without seeing it, it doesn't sound like a factory-original gun. The top levers on the NID are on the stout side compared to, say, a Parker and I shouldn't think they would require any hardening at all to do service. The barrels - they do come apart and I would suspect that most of the folks visiting this site have had a set resoldered at one time or another. Keep in mind, too, that it is not wall-to-wall solder under the ribs. Beyond that, it's not like the guys at Ithaca never soldered barrels; Ithaca's reputation was sufficient enough that they sold upwards of a half million doubles - might you have a set of (semi) resoldered barrels. Still, you might have inherited a perfect storm of inattention.