Those double link Colts, and some others (e.g., the Webley 1913) in that general period, did have bronze firing pins, and the ones you got from Numrich are Colt originals, not repros. I am not sure why brass/bronze was used, but it may have been out of concern for a firing pin rusting in place with the corrosive primers and the powder fouling of the time.
FWIW, I didn't think beryllium copper existed in 1903, but some single actions of the 1960 era had parts like the cylinder stop made from that material. It was touted as a miracle metal, but proved too soft for any part that would take an impact.
On that repro pistol, I suspect the firing pin is of some light weight material used to avoid installing a firing pin block. If a 1911 type with the chamber loaded is dropped on the muzzle, the standard firing pin can creep forward and fire the round. This condition was unknown prior to the use of full length guide rods, since in the original pistol the barrel and slide would move back, absorbing the shock. But with a FLGR, there is nothing to absorb the blow and the gun can fire. California rules say an auto has to be made not to fire under that condition, so Colt and other makers worked up firing pin blocks to prevent a problem caused by the FLGR. So a phoney solution to a non-existent problem caused a real problem and ended up costing every gun buyer money.
Last edited by James K; May 20, 2010 at 10:24 PM.