If you are going to collect US wings and insignia, the very first and most important lesson you NEED to know is how to tell a cast from a die struck wing. 

First, a bit of a primer on the difference between cast and die struck wings.  Most (about 99.99%) of US insignia were made using die struck techniques.  Briefly, a large press was used to forcefully press (up to a few tons of pressure could be generated) a metal planchet into a die containing the shape of the badge.   This is basically the same process that is used to mint coins.  Sometimes the part of the machinery (the “forcer”) that forced the planchet into the die was used to impart markings to the back of the badge; these markings could be in relief (standing up from the surrounding material, produced during the stamping process), incuse relief (markings standing up from a surrounding lowered area, usually square or rectangular (Balfour used this on some of their wings) or incised (stamped into the wings).  Frequently, a hallmark or STERLING mark were put on the wing in this manner.  Once the wing was struck, it has excess flash all around the perimeter of the badge that needed to be removed, typically with a special tool that “trimmed” the metal  that frequently left many small “shear marks” along edge of the wings.    Finally, the wings were further processed for quality control, had their hardware attached, and underwent their final preparation for sale (I wont cover that process now).  Because of the large forces used, special equipment was required to die struck wings as well as carefully carved and prepared dies to withstand the high pressures involved.

Thankfully for us (collectors), this means that die struck wings have characteristics of manufacturing that help us tell them from fakes, and perhaps even more importantly, it is rather difficult (sadly not impossible) for fakers to make die struck wings.

So, you may ask.... what are the characteristics?

1. 1) Die stuck wings, like coins, usually have very sharp and clear detail.
   

2. 2)The energy used to generate the wings impart tremendous forces, and thereby compresses, strengthens and hardens the metal.   Importantly, the resultant die-struck badge has a different feel and size from a cast badge (discussed below).
   

3. 3) The trimming of the excess flash tends to leave small perpendicular lines on the edge of the wings.  Sometimes these are polished or buffed off, but a careful study of the edges with a 10X loupe will still find traces.  One trick to to carefully look in areas that are protected or hard to reach.
   

4. 4)All the wings made from a die should be identical (minus any wear or dings that came later) to each other.  this makes it especially important when comparing “known” originals with “suspected fakes”.  For example, cast wings are always slightly smaller than die struck wings, as illustrated below.
   

Second, a bit of a primer on cast wings.  It is “common” knowledge that most CBI and POW wings are cast.  Actually, this is not true at all.  Most CBI wings were made by modified by hand cutting and carving a metal planchet.  Very few, if any CBI wings are actually cast.  On the other hand, it is true that POW wings were cast, frequently using tin/lead from the Red Cross packages.  Still, these wings are so rare, that they won’t be really a factor in most collections.  So, let me stress, just about ANY CAST WING IS A FAKE! 

How are cast wings made?  In my humble opinion, the casting process of wings has evolved greatly over the years.  I suspect the first cast wings were simply made by taking an extant wing and making an impression in find sand or plaster.  The wing was removed and molten metal was then poured into the mold and left to harden.  As the metal cooled, it shrank and the impurities came out.  This left a poorly detailed wing, with all sorts of flaws in the metal--these flaws will resolve as small pits and craters in the metal that are clearly seen by a 10X loupe.  These early attempts at casting wings are pretty easy to identify, because of the general softness of detail and the pits and small imperfections and “wavy” finish that you see in the metal.   Frequently, the faker will try to cover these flaws by heavy grinding or finishing of back of the wing.

Later attempts at casting used a centrifugal method.  In this process, a mold was set up and then spun in a centrifuge.  The forces pushed the metal up against the front of the mold and gives pretty good detail at first glance.  However, the molten metal still shrinks, and many details are lost.

So, to recap, cast wings are:

1. 1) Are always smaller than their die struck brothers.
   

2. 2)Lack sharp, well defined detail.
   

3. 3)Usually have obvious impurities in the metal that leave pits, craters and “wavy” finish.
   

4. 4)Lack the small perpendicular lines from the trimming of excess flash seen on die-struck wings.
   

This is just a primer, and much of the art of telling die-struck from cast wings only comes by handling lots of wings.  Some die-struck wings seemed to have been poorly made and wear and tear on the wings can make them look cast.  Some cast wings are well made and very VERY hard to tell from the originals.

Below, you will find  a slide show with some examples of what I have been talking about.