8¢ - Olive green, deep olive green
Printing Method: FLAT PLATE
Subject: George Washington
Number issued: 94,000,000
Perforations: P12
Watermark: Double Line USPS
Scott #: 337
Issued: December 12, 1908
Used
$2 - $4
No postmark with gum (MH)
$10 - $30
Full perfect gum, no postmark
no trace of stamp hinge mark (MNH)
$80 - $120
#337 was issued with the following plate #'s
Imprint and number
4919-24
An illustration of the double line USPS watermark found on this stamp
Sometimes you will see very expensive copies of #337 advertised as experimental paper or CHINA CLAY PAPER. There is no such thing, what exists are stamps which have "dirty water" paper because silica in the water became embedded in paper produced during drought conditions when the mill pond was low.
There are some old PF certificates still around that state that a stamp is a "China Clay' stamp. The PF no longer recognises China Clay stamps and has ceased certifying them.
Do not be tempted to buy something that does not exist.
The US was a member of the Universal Postal Union (UPU) and under the terms of the agreement each member was required to send a copy of a new design to all the Universal Postal Union countries. Today, most countries still have these samples. Portugal does not, it distributed its samples long ago. Portugal overprinted all their samples with the word 'Ultramar' which translates to 'Specimen'. For the whole of the period of the production of the Washington Franklin series only one example of each value was sent to Portugal, therefore finding one is not easy.
Finding #337 on cover is hard. This from 1912