I have two .375 Winchesters. One Marlin, other Savage. The Savage a Model 99A and supposedly “collectible”. Not mine! Bubba having wacked the barrel to 16″! Almost surely a fire breather. A surprise to me, comment above concerning ammo costs. Wow! But also, I’ve read negative reviews of the cartridge performance and now, with ammo costs, a double whammy for other than perhaps collectors.

Bringing me to the matter of your interesting Win 375, big loop. Without some kind of factory variation/custom shop documentation, presumptively “aftermarket” modification. Moving to the category buyer who, as me with some of my rifles, appreciating such variation more in terms of interesting feature(s) value.
I have one large loop lever. Factory and frankly a package deal with a rifle I did want and ultimately cheap for both. Beyond publicity in the now ancient TV program (was it “Rifleman”?) and lever twirling demos, myself seeing no practical use and rather detrimental practicality in such large loops. Don’t think I’m alone in such view. I’m sure there’s a market for your rifle, just with no idea where. Exposing for sale perhaps at the going price for a comparable price normal factory model.
I think you may have a couple of problems marketing. First just my personal prejudice, but as noted practical use the large lever loop wanting. I do have a Model 94 “Wrangler”, 32 Win Special with such style. Bought it too, new condition for a song and that the only reason! My lever loop looks different from yours and I’m wondering if yours even quite the factory pattern. Without Winchester confirmation of factory/custom shop, seems to me likely source of value excluding collector interest.
I’m only with something of a last residual answer. One I hate, essentially begging the question. “Whatever you can get for it.” Needing that special buyer, desiring. Myself with more than a few acquisitions in that category. Intentionally. Just ‘liked them’ for what they are, but integral – needing the “bargain” aura in relationship to negative mod(s).
Good luck and…
Just my take
John