Growing up in the 50s and 60s when the reenactments began, in an area that was heavily invested in the tourist trade, every gift shop in this area had a box of these.
They sold them for .25 a piece and were all heavily encrusted with lead oxide. I always believed they were newly made and aged to look old. I've also know of hunters who've found whole cases of ammo buried by retreating troops. That happened a lot here in the northern valley where the real estate changed hands
many times. One of my friends found such a cache in the middle of a Rt 66 cloverleaf! Buried by the Union troops in their retreat from Front Royal, Va May 23, 1862. Recognized as the first engagement of Stonewall Jackson's Valley Campaign.
Best wishes and good luck!