Dan, I got your email and decided to answer it here for the benefit of all.
1st R15 2cent Orange,
IS Known Imperf and Part Perf. However, their are so few legitimate copies known that Scott has never acknowledged it with a price. Before I would render a guess I would want to know the measurement of the top and bottom imperforate area's. I will say that 1868 would be VERY late for one to be cancelled. I would be happier with an 1864 or '65 cancel. measure from the lowest point of the printed area on the bottom to the edge in at least 3 places and let me know. On the top the same only from the top of the design of course.
2nd R33 10cent Certificate. Cancel is correct date wise for it to be possible. However, I would not accept it as the margins are
WAY to close for comfort on a $700+ stamp.

I highly doubt it would get a good cert. that would be the only way I would accept it.
lastly R35e 10cent Ultramarine Foreign Exchange.
Fake Forget margins, Cancel or any other reason other than it came out after all of the 1st issue stamps were issued with complete perforations (4 sides).
A very condensed short little history: In a rush to produce enough stamps to fill the needs of the US Gov't. Buttler and Carpenter shipped a quantity of stamps both Imperforate and partly perforated to the USIR.