Experimental fractional currency notes were never meant for circulation. These notes were produced so that the Bureau of Engraving and Printing could test the use of different papers and printing processes. Essay notes were printed with subtle differences such as color or a slight change in the detail of the note. An experimental note used different color lathe or other styles. The Bureau was in search of the ideal combination of ink and paper. At the Bureau, many of the notes were cut in half or had their edges cut off, and then they were soaked and dried repeatedly to test how well the paper would hold up to extended circulation.
Generally these notes were printed on only one side like specimens notes. Many of the reverses would not be blank but have surcharges or bronzing on them. Most were narrow margin varieties but some wide margin examples were made but are extremely rare. The experimental notes were punched canceled with two semi-circular holes and then stamped with a purple "specimen". A few of the note were never punched nor stamped and these too are extremely rare and some had more than two holes or used smaller circular holes.
Most experimental notes are of the Second Issue but there are also a limited number of Third Issue examples and these demand a high value when auctioned. The Second Issue notes can be found with or without the bronze surcharges. The unbronzed varieties are seen as more rare than their counterparts. Also the reverse notes are considered more rare than the face notes.
It is hard to estimate the values of the experimental notes. It was estimated that 50-80% of the experimental notes were owned by Milton Friedberg. When CAA sold Milt's entire collection of fractional currency, his experimental notes were at the end of the auction. Many of the floor bidders had exhausted their money reserves and many of these notes went for much less then their estimated values. When 50-80% of the experimental notes were sold at one time, it became a saturated market. Generally most of the more common experimental notes will sell between $150 - $400 and the rarer Third Issue notes will go between $2000 - $5000.
In the five cent note shown to the left and below, please notice the cancelation stamp and the holes punched. Also notice that the paper was varied from plain paper to fiber paper and in this example, the plain paper note being much more rare than its fibered counterpart.