The best, and probably only, reference for this type of material is "An Illustrated History of U.S. Loans" by Gene Hessler. I was able to trace your coupon to the Four Percent console bonds first issued in 1878. Unfortunately there is no image of the $50 bond in the book, though there is an picture of your coupon. Fortunately, I was able to find one on Wikipedia.
The book gives the registered $50 bond a rarity of R7, meaning an estimated 4 to 12 of these remain in existence. So coupons are a lot easier to find -- and unlike most commercial bond coupons, they do carry some value.