Joel, I lived in Ft. Wayne for many years and went through all the local old directories back in 1996-97. This is what I found on the two Lade brothers in Ft. Wayne.
Source: "1876 Indiana Historical Atlas" - G. Lade and Max Lade were from Germany and arrived in Indiana 1872; they may have been in America earlier than when they arrived in Ft. Wayne, IN.
Lade, G. - Allen Co., IN, Ft. Wayne - Gunsmith (p. 333)
Lade, Max - Allen Co., IN, Ft. Wayne - Engraver (p.333)
G. Lade & Bro., "Gunsmiths & Engravers, Importers and Dealers in Sporting Materials generally." This advertisement is found under "Allen
County, Ft. Wayne, p.415
They do not appear in any "Ft. Wayne City Directory" until the 1874-1875 directory by Polk, Murphy & Co. Listed under "Gunsmith" in the 1874-1875 Ft. Wayne City Directory is the following entry:
Gustoff Lade, 63 E. Main, boards 91 Washington St.
Fort Wayne City Directory 1875-1876, by R. L. Polk & Co. has the following listing under "Gunsmiths":
Gustave Lade & Bro. (Gustave and Max), gunsmiths, S.W. Corner of Columbia and Clinton Streets.
Fort Wayne City Directory 1876-1877, by Edmonson, under "Gunsmiths":
Gustave G. Lade, Gunsmith, Engraver and Liquor Dealer, 26 E. Columbia Street, residence same.
Max G. Lade, Gunsmith, 36 Clinton, corner Columbia, residence at 73 Harrison Street.
Fort Wayne City Directory 1877, by R. L. Polk & Co., under "Guns, Pistols, Etc":
Max G. Lade, Gun & Locksmith and Engraver, and dealer in guns, etc. 58 E. Main, same residence.
Fort Wayne Business Directory 1880, has following listing:
Max. G. Lade, 58 E. Main Street, arrived in 1874 from Germany, Importer Wholesale & Retail, Dealers in Breech & Muzzle Loading Guns, Revolvers, Fishing Tackle and Ammunition.
That is the total extent of material on Max and Gustave Lade, gunsmiths of Ft. Wayne, IN that I was able to locate in local records through 1880...and I did a pretty through search for gunsmiths. Max G. Lade was recorded as a gunsmith in local directories until 1885...don't know if he went into an other line of work, died, or moved after that date. Hope this helps with your rifle. I will mention your rifle to my friend, Jeff Jaeger, who is working on a reference book on Indiana gunmakers. He may want to contact you for additional information on your rifle after he learns about the name, city, and date all together on your gun...since that type of "documentation" makes it a useful and/or valuable piece for research purposes. Shelby Gallien