10c Green, Ty. III/II
(15/14). Vertical combination pair, large margins to just touched at
lower right, rich color, tied by "New Orleans La. Dec. 16" circular
datestamp on light blue folded cover to Vera Cruz, Mexico, clear "2"
(reales) handstamp for internal Mexican postage, sender's ship designation
"p. Calhoun" and blue oval backstamp, file fold with few tiny
erosion spots, still fresh and Very Fine
(Image) 
10c Green, Ty. III (15).
Horizontal strip of three, full to large margins, gorgeous deep shade, tied
by contrasting vivid red grids, matching "New Haven Con. Jan. 15,
1856" circular datestamp on thin tissue-paper cover to Munich,
Bavaria, "Boston Br. Pkt. Jan. 10" transit backstamp, red "7" credit
handstamp, red framed Aachen transit (Jan. 29) and Munich receiving
backstamp, with original enclosure, few small edge
improvementsEXTREMELY FINE. A COLORFUL COVER AND SUPERB MULTIPLE OF THE 10-CENT 1855 TYPE III PAYING THE 30-CENT PRUSSIAN CLOSED MAIL RATE TO BAVARIA.
Ex Hill (Image)
10c Green, Ty. IV/II
(16/14). Positions 65/75L1, vertical combination pair, top stamp Type
IV recut at top, huge margins all around including part of adjoining stamp
at top (55L), which shows recut bottom line, used with 1c Blue, Ty. IV
(9), recut at top, ample to large margins, rich colors, tied by grid
cancels and red "New Orleans La. Aug. 28" circular datestamp on 1855 folded
letter to Bordeaux, France, red "New-York Am. Packet Sep. 5" transit
datestamp, Calais transit and "8" decimes due handstamp also ties stamps,
London transit (Sep. 17) and French receiving datestamps on
backEXTREMELY FINE. ONE OF THE FINEST COVERS KNOWN WITH THE 1855 10-CENT TYPE IV PAYING THE 21-CENT AMERICAN PACKET RATE TO FRANCE.
This cover was carried on the Collins Line Pacific from New York (Sep. 5, 1855) to Liverpool (Sep. 15). It was prepaid 21c for the American Packet rate and treated as a single-rate letter in France (8 decimes due). This is an early use of the 10c 1855 Issue.
Pencil notes on back in the hand of Dr. Carroll Chase, who notes "Superb vertical pair". Ex Grunin. (Image)
12c Black (17). Large
margins to slightly in at sides, used with 1857 Perforated 12c Black
(36), Plate 1, superb centering, tied by vivid red grids,
matching "New York 19 Aug. 5" credit datestamp on small cover to
Gloucestershire, England, bold red "America Liverpool Paid AU 16 57"
transit datestamp, with original enclosure, Very Fine, an extremely rare
combination of imperforate and perforated issues of the same denomination,
also a very early 12c Perforated usage (possibly the earliest
transatlantic) (Image) 
12c Black, Diagonal Half Used
as 6c (17a). Lower left diagonal half with ample margins, tied across
all sides by bold "New-York Sep. 9" circular datestamp on buff cover from
San Francisco to Honeoye Falls N.Y., bold red "Via Nicaragua/Ahead of
the Mails." framed handstamp, small sealed opening tear at top left, minor
wear and soilingVERY FINE. A RARE EXAMPLE OF THE 12-CENT 1851 BISECTED AND ACCEPTED FOR 6-CENT TRANS-CONTINENTAL RATE ON COVER MARKED 'VIA NICARAGUA".
Ex Brown. With 1982 P.F. certificate ("genuine usage") (Image)
12c Black, Diagonal Half Used
as 6c (17a). Upper right diagonal half, even margins just into outer
frameline, well-tied across the cut by "New-York Mar. 1" circular datestamp
on 1853 folded letter from New York City to Philadelphia, sender
wrote addressee's name incorrectly and erased the first lineVERY FINE. AN EXTRAORDINARY USE OF A 12-CENT 1851 BISECTED STAMP FROM ONE MAJOR EAST COAST CITY TO ANOTHER, PREPAYING THE DOUBLE 3-CENT DOMESTIC LETTER RATE.
The majority of 12c 1851 bisects are found on transcontinental covers, usually applied in California. Only a small number of intra-East Coast usages are known.
Ex Sheriff. With 1980 and 1986 P.F. certificates. (Image)