Civil War envelope showing Union gunboats attacking Confederate fort with message "Our gunboats attacking the rebel forts"

Addressed to Mr. Dyer Seely, Moscow, Hillsdale County, Michigan; postmarked Lexington; bears 3 cent stamp."
Stamped on verso: "U.S. Pension Office, Sep. 7, 1888."
Notations on verso: "Middle no. 367,890," "Amanda F. Seeley, mother of Frederick D. Seeley, B"18" Mich. Vols.," "Filed by Geo. E. Lemon, Washington, D.C."
Probably sent by Frederick D. Seeley of Co. G., 18th Michigan Infantry Regiment, who was killed in the explosion of the Steamer Sultana on the Mississippi River, April 27, 1865.
Deposit; Tom Liljenquist; 2018; (D074)
Purchased from: Jack Hurov, August 2018.
pp/liljmem