3c Executive (O12).
Well-centered, bright color, tied by bold strike of quartered cork,
"Washington D.C. Apr. 30" circular datestamp on Executive Mansion imprint
cover signed by O. E. Babcock (Secretary to President Grant) to Edward
Pierrepont in New York City, 1875 docketing at left, small cover tear at
top from opening, Very Fine, the Executive stamps were issued July 1, 1873,
were supplanted by penalty envelopes on May 1, 1879, and were declared
obsolete on July 5, 1884 (Image) 
3c Executive (O12). Tiny
perf creases, tied by cork cancel, blurry "Washington D.C. Jun. 20"
circular datestamp on Executive Mansion imprint cover to New York City,
endorsed "U.S. Grant", backflap removed, otherwise Very Fine, ex
Griswold (Image) 
3c Executive (O12).
Centered to left, tied by fancy cork cancel and "Washington D.C. Mar. 18"
circular datestamp on Executive Mansion imprint cover with signature of
Grant's secretary, C.C. Sniffen, includes original 1874 2pp autograph
letter signed from Sniffen on behalf of the President, to a Col. Swift,
declining an invitation to the reunion of the Michigan Soldiers & Sailors
Assoc. at Jackson, Mich., cover with edge wear and some soiling, otherwise
Fine, ex Griswold (Image) 
6c Executive (O13). Tied
by cork cancel, "Washington D.C. Jul. 30" (1877) circular datestamp on
Executive Mansion imprint cover to Attorney General Edward Pierrepont in
London, England, red London Paid and receiving backstamp, 1877
docketing at leftFINE AND FRESH. A VERY RARE USE OF THE 6-CENT EXECUTIVE DEPARTMENT STAMP ON COVER TO ENGLAND MAILED DURING THE HAYES ADMINISTRATION.
The 6c treaty rate to England was superseded by the 5c GPU/UPU rate in July 1875. Thus, the 6c Executive stamp overpays the required postage by 1c. Only seven 6c Executive covers are reported in Markovits catalogue (Bennett).
Ex "Crystal" (Ehrenberg). With 1981 P.F. certificate. Scott Retail $3,500.00 (Image)
John Hay. Private
Secretary to Abraham Lincoln as President, free frank "John Hay" on
"President of the United States, Priv. Sec." imprint cover to Syracuse
N.Y., neat "Washington D.C. Nov. 9, 1863" circular datestamp, some overall
soiling, Very Fine free frank from Lincoln's personal secretary, Hay, also
a lawyer from Springfield Ill., who later became Secretary of State under
McKinley and Roosevelt (Image) 
John Nicolay. Private
Secretary to Lincoln as President, free frank "Jno Nicolay" on
imprint cover from "President of the United States, Priv. Sec." to Auburn
N.Y., well-struck "Washington D.C. Jan. 15" circular datestamp, Very Fine
(Image)