A Berford & Co's Express cover bearing two pairs of the 10c Violet has seen the highest bids in Spink Shreves' Collector's Series sale, held on August 15 in New York.

Berford & Co's Express was one of many private mail firms, such as the famed Pony Express, operating between the US' east coast and the remote west in the mid-1800s

Dating to 1852, the cover sold for an impressive $35,000.

Berford & Co's Express was a private mail company founded by Richard G Berford in San Francisco in 1849. It operated between the US coasts, boasting offices in San Francisco, Sacramento City, San Jose and Stockton, before closing in 1855.

The cover bears one horizontal tete-beche pair of the 10c Violet from the company, alongside a 10c vertical pair. Both pairs have large margins and are in superb condition.

The Robert E Lee letter was mailed during the early day of the Confederate invasion of the north, which culminated at Gettysburg

Also selling, at $26,000, was a field cover from Confederate general Robert E Lee, which is considered to be among the finest and most attractive of its type.

Addressed in his hand to "Mrs Margaret B Dangerfield, Ingleside, Amelia Court House, Virginia," it bears a Confederate States 10c milky blue from Die A, which is tied to cover by a "Richmond, Va/Jun 14, 1863" datestamp.

The cover's value was enhanced by the fact it was sent during the early days of the Confederate invasion of the north, which culminated in the historic Battle of Gettysburg.

George Washington free franks in this condition are extremely sought after

Also starring was a cover sent from George Washington during the revolutionary war to Joseph Hewes of North Carolina, a signer of the Declaration of Independence. Signed "G. Washington" and in remarkable condition, aside from a vertical fold at the centre, it made $18,000.

Paul Fraser Collectibles has some of the finest stamps for sale.