The document that establishes this storied baseball franchise as a real corporation. Establishes it as part and parcel of the Metropolitan Exhibition Company, and hence a National League franchise. Incredibly important handwritten letter is dated from "Providence" December 6, 1882. On Hotel Dorrance stationery, "The Metropolitan Exhibition Company, a corporation duly organized under the laws if the State of New York, hereby guarantees any and all engagements that may be made by and between the New York Ball Club of which John B. Day is President and Charles T. Dillingham is Secy. & Treasurer, or by their authorized agents, with the National League of Professional Base Ball Clubs or with the clubs thereof. The Metropolitan Exhibition Co. by John B. Pres. (signed)." A supremely important baseball document. Condition is excellent (8.5x5.5"). Ex-Barry Halper Collection.