Here's a 3 digit serial number M1910 .401 WSL, made in 1910 of course, that I picked up on Gunbroker for $202. Price shows the lack of interest in these early self loaders. 200gr bullet with 2000 ft lbs of muzzle energy-the Winchester ads of the day stated "Hits Like a Krag" and "Hits Like The Hammer of Thor".
I picked up an M1907 .351 4 digit serial number (made in 1907) in Vermont for $175 at a small gun shop while visiting. The .401 came from a seller in Massachusetts, and it's fairly well known that the WSLs are pretty common in the northeast due to them having been considered handy moose, deer and bear rifles out in the timber.
They were among the most advanced arms of their type during their time, but most of the people that used these WSLs are gone now. The book written about them is called "The Forgotten Winchesters" (go figure) and there is no mention of them on the Winchester collectors website.
But they are efficient, reliable and I'll agree that they are plenty accurate at normal woods hunting and gunfight ranges. I often say "The only jam you'll get with a WSL is on your toast."
Sometimes, over engineering is a positive thing.