I spent last evening viewing videos on the process Despiau uses to manufacture their violin and cello bridges.  It is a very small operation (about the size of a two car garage).  I was amazed to find that they sand the angle of the front surface of the bridge.  Despiau is coy about how they produce the “heart” features of the bridge, but it appear to be either routed or punched since splinters are left until further finished (if anyone has further knowledge, I am very interested).

I have never seen so many bridges dropped, fingernail scratched, and otherwise manipulated for sound.  The owner of the company said that an inexpensive electronic scale is completely necessary for bridge selection.  A light 4/4 violin bridge (5 gram and less) will produce a mellow sound and is good for orchestra play.  A heavy (6 gram and more) bridge will have greater projection and be more bright, and will be favored by the soloist.  Those in between must be a mixed bag (my opinion, he did not go into them).