3c Ultramarine (114).
Horizontal strip of three and single, used with two 3c Red, F. Grill
(94), tied by cork cancels, "Brownsville Tex. Nov. 15" circular
datestamp on registered cover originating in Monterey, Mexico, and
mailed at Brownsville to Charleston S.C., letter states that gold is
enclosed to secure a subscription to a newspaper ("I do not want a
Radical paper"), sender's blue oval datestamps (Monterey Nov. 4, 1869)
on front and back, along with remnants of red wax seal, stamps prepay 3c
postage plus 15c registry fee and were applied by a forwarder in
Brownsville -- mailing instructions in letter identify forwarding agent as
A. Marks -- stamps have faults, cover has some wear and slight toning,
nonetheless a Fine and very presentable cover, extremely rare example of
valuable mail crossing the U.S.-Mexican border and entering the post office
as a registered letter (Image) 
3c Ultramarine (114).
S.e. at left, tied by cork cancel and "Boston Mass. Aug. 12 3 PM" circular
datestamp, used as forwarding postage with Hawaii 1864 2c Rose Vermilion
(31), horizontal strip of three, pen-cancelled, tied by target and
lightly-inked strike of red "G.P.O. Honolulu Paid All" double-circle
datestamp on cover to Boston Mass., forwarded to Bethlehem N.H.,
bold "San Francisco Cal. Aug. 5 Paid" magenta transit circular datestamp,
strip with faint scrapes probably from the Honolulu clerk's attempts to
cancel it with a dry penVERY FINE AND EXTREMELY RARE COMBINATION FRANKING DURING THE UNITED STATES-HAWAII TREATY RATE PERIOD.
After the 6c U.S.-Hawaii treaty rate became effective, mixed frankings were necessary only to forward letters (as in this case) or to send letters addressed beyond U.S. borders. (Image)
3c Ultramarine (114).
Horizontal pair, s.e. at left, perfs in, used with Canada 1870 3c Red,
Small Queen, Ottawa Printing, Perf 12 (37), horizontal pair, small
faults at top where placed over edge, both pairs tied by circle of wedges
and red exchange office circular datestamp ("Apr." clear, but New York or
Boston city name is too faint to determine) on small narrow cover to
London, England, red London Paid receiving datestamp with 1870 year
date, opened on three sides, crease at left clear of stampsVERY FINE. THE ONLY RECORDED COVER WITH THE 1869 PICTORIAL ISSUE USED IN COMBINATION WITH CANADA STAMPS. A REMARKABLE COVER.
The first 3c Small Queen stamps were issued in January 1870 from the Ottawa printing. This April 1870 cover bears a pair from the early 1870 printing. There are no Canadian postal markings, therefore, it appears that this cover was first franked with Canadian stamps for the 6c rate to England, then franked with United States stamps for the corresponding rate to England from a United States origin point. The cover was probably carried outside the mails to Boston or New York and mailed from there. It is the only U.S.-Canada mixed-franking cover recorded in the Forster census of 1869 mixed frankings.
Ex Ishikawa. (Image)
3c Ultramarine (114).
Grid cancel, matching strike and "Detroit Mich. May 24" circular datestamp
on 3c Pink entire to Victoria, Canada, 1869 receiving backstamp,
Extremely Fine (Image) 
3c Ultramarine (114).
Vertical pair, deep shade, tied by quartered cork cancels with duplex "San
Francisco Cal. Nov. 30" circular datestamp on 1869 yellow corner card cover
to Cambridge, New Brunswick B.N.A., transit datestamp at lower left,
transit and receiving backstamps, Very Fine
(Image)