master hub: A metal punch used to produce "master dies." See also hub and master die.
Matte Proof: Especially U.S. gold coins of 1908 to 1916, coins produced from dies entirely sandblasted with no mirror surfaces. See also frost and Proof.
Master hub - The original hub created by the portrait lathe. Master dies are created from this hub.
Matte proof - A proof coin with a grainy surface appearance produced by dies treated to obtain a minutely etched surface.
MASTER HUB The original hub made by the Janvier reducing machine from the galvano or model of the coin to be produced.
MINT (1) Establishment which produces coins. (2) To strike coins.
MINTAGE Quantity of coins struck.
The master hub is then placed into a hydraulic press, known as a hubbing press, opposite another blank steel bar. These steel bars, usually about 6 inches long, are hardened steel.
The master hubs and dies for this coinage were prepared by the United States Mint's Chief Engraver, Charles Barber. He worked from designs submitted by Spreckels and subsequently modified by Mint Director Horatio C. Burchard.
The master hub is then used to make master dies. This process is called "hubbing". Using a hydraulic press the master hub is pressed into a piece of die steel to produce a master die.
Because making the Master Hub takes a lot of time and work, it is used very few times.
master die The main die produced from the master hub. Many working hubs are prepared from this single die. master hub The original hub created by the portrait lathe. Master dies are created from this hub.
*Some of the 1998 pieces also exhibit the so-called "Phantom D" Mint Mark; slight traces of the Denver Mint Mark that were left on the the 1998 Lincoln cent master hub, modified for use as a Philadelphia hub.
Next, a Janvier reducing lathe takes several days to reduce the image onto a steel master hub in a process that has not changed in over a hundred years. The master hub is then tempered to make it hard.
Barber's coinage coincided with an innovation in manufacturing master hubs. Large cameo models were made out of wax and a resinous gum, then electroplated.
The original coin image is actually a plaster sculpture about 8 to 12 inches in diameter, from which a Master Hub is created using a special process that reduces the image to actual coin size.
galvano
An epoxy coated plaster relief model of a coin created in order to produce master hubs, which in turn produce coin dies.
grade
Condition assigned to a coin mainly in an effort to determine its relative value.
"On the question of which elements were in the model and which were entered at the master hub or master die stage, ...
If on the other hand, the design is beyond the die's face, (this is a hub or the master hub from which more dies can be made), the resultant coin will have an incuse or intaglio design.
The drawback, however, was not only an artistic loss, but the weak design elements required periodic alterations to the master hub.
by a company from Birmingham, England, as an eagle hub bearing this name is mentioned by Don Taxay as possessing an English pedigree. Denominations of $2½, $5, $10, and $20 are known in silver, copper, and white metal. The master hub is ...
A transfer lathe copied the elements of a larger electroplated wax and gum model to a master hub the size of the actual coin. This allowed for greater precision, thus more detail and more design elements.
 See also: Mint, Coin, Struck, Coinage, Dollar
  
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