We might be wrong but I can confirm that your observations and investigations match mine, Carol. Took a bit of digging on the WN abbreviation, tho' it was the second area to occur to me after Wisconsin :lol: .
I still reckon a careful charcoal rub will give us more details on the stamp - if only I could fly over and do it myself ... {looks around for people to make offers to pay the air fare ... :lol:}. The top arc is likely to be a company name I reckon - the "co." at the end rather suggests that to be the case at any rate.
I agree; I'd guess the company name ends in "uss", as well... though I wonder if that "uss" could be "***" as in "brass"?