There seems to be something wrong with that s/n as Winchester made only about 160000 of these rifles ( I'm not including the recent release by Winchester of this model in, I believe, 45-70 only).
The 50-100-400 was a very rare caliber for this firearm and as such commands a premium. Other options that command a premium are case coloring, takedown feature, checkering, octagon barrel, ect. The condition of the firearn is also very critical. The value of this firearm could range anywhere from $1000 to $15000. As I'm sure you know this happens to be a very collectable firearm and getting a couple of collectore in a bidding war for a very high condition one should not be to difficult.
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