I would bet that's even more unusual. I know that was available in the custom shop during the late 90s and early 2000s(stainless and wood, unsure of when they began and dropped 300 RUM), but I think it was also available briefly as a production item in stainless and wood. I bought mine in 2002. Is yours called the stainless sporter?
And I've also had people tell me that Winchester never made these, but they just tend to be overopinioned, underinformed types.