For today's 'what the heck?' cover (see below) I could use some help in identifying the stamp. The cover was mailed, according to docketing, in 1854, from Plymouth, MA to Burlington, VT. The stamp is tied by a nice, blue Plymouth cds next to which is a black Burlington cds presumably applied when the cover was forwarded to a town I can't decipher.
The stamp clearly has only single vertical frame lines, making it a Type I, either a 10 or 11. The color just doesn't look right for a #10, but... the #11 wasn't issued until July of 1855, a full 7-months after the docketing on the envelope.
So...I'm looking for a opinions. Is this a #11 with bogus docketing? Is it a number 10 even though the color is a bit "off?" Any help greatly appreciated !!