Winchester 1873 Heavy Barrel questions|Winchester Rifles|Forum|Winchester Collector

I’ve found locally a 3rd Model 1873. This was a few weeks ago and still present at the shop and it’s somewhat tempting but I’m unfamiliar with this variant. If memory serves it’s an 1888 production year. Barrel length is probably 24-26” rifle configuration with full length mag tube. It almost looks awkward to the barrel diameter. Initially until heaving of the heavy barrel version I assumed someone rebarreled it(still wondering that honestly). It has no markings on the barrel besides the 44WCF markings. No Winchester/address, etc. it looks like it’s been reblued at some point and functionally is in good shape. Wood shows no cracks and the bore looks great. Part of why I’m suspicious. Almost too nice compared to any of my other original Winchesters from the time. My biggest hold up is rust. It has several areas where someone got on it and caused rust to the point of pitting. Nothing to effect use and it’s still certainly restorable but it’s worse than many I’ve saw before. I’m wondering if there’s a way to prove it’s a factory heavy barrel and where to begin valuing it. I know the owner and probably get it for under 1500.