BTW SC Loyalist, you hae several stray caps in that tin. UMC and Remmie caps were all ridged You have at least 6 that are not ridged.
Goldmark IIRC was a hungarian who discovered the ignition properties of red phosphorus. He recieved one of many patents for percussion caps. Goldmark was eventually purchased by Winchester, which was in turn purchased by Western Powder. In 1935, Winchester and Western became divisions of Olin Industries. Stoeger's sold Goldmarks caps in their 1947 cat. The 1952 cat indicates that percussion caps were unavailable. So, the picture below dates the caps as manufactured after 1935. I would think that by 1935, the Winchester Western Olin companies would know the difference between primers and percussion caps.
They are definitely not Berdan caps which are slightly wider in diameter and only half as deep. I have reloaded some original 43 Spanish cases with Berdan primers. They are nearly 2x's the diameter. Regular boxer primers have an integral anvil pressed within the tiny cup. Berdan cartridge cases have a wider hole for the primer to be pressed in and the center of the hole has an anvil (a hump shape) with a few tiny flash holes around the hump. The Berdan primers I used, were ordered from Old Western Scrounger years ago. They looked like they were painted with green lacquer inside.
I too have had instances of the foil and fulminate coming out of the caps, but I have had the same with Italian non foil lined caps also. On one occasion I saw the fulminate and foil stuck to a nipple after the copper cap was removed. The gun, an old double still fired.
In his book the Gun and it's Development, W. W. Greener stated that the first centerfires came about in the 1830's and he specifically mentioned the Dreyse needle fire system and a few other breech loading combustible cartridge guns.
The early Maynard breech loaders used a cartridge case that had a modern style flash hole, but no primer pocket. When the break open gun was loaded and closed the flash hole was directly under a percussion nipple which was in line with the flash hole and bore. Similar to a single shot shot gun, but with a percussion nipple where the firing pin normally is on single shot shot guns.
I have checked in several of my gun books and can't find an explanation. I talked to a guy that identified himself as an assistant curator at the Smithsonian and he knew less than I do.
I do have a motive, aside from idle curiosity. Pa hunting regs for the regular deer season say I can use any manually operated center fire rifle or handgun. It does not require a center fire "cartridge"
To my way of thinking, center fire is just a type of ignition, like a match lock, wheel lock, pin fire, rim fire, etc. Ignition is not dependent on where the gun loads, whether it loads from the front, the breech, or somewhere in the middle, like the Hall and Green carbines or cap and ball revolvers. On an English firearms auction site, there was a breech loading cartridge flint lock. It was a break open design and each cartridge had it;s own flash pan and frizzen. Like wise, there were break open style breech loading percussion arms, some took paper cartridges like the Sharps, some took iron cartridges which contained a percussion nipple in the base and used a box lock hammer to strike them. They were indeed, like the first Gatling gun ammunition, percussion centerfire. If a percussion nipple lines with the center of the chamber, and the chamber contains the powder and ball, does a cap and ball revolver also qualify as centerfire. Does a preloaded cylinder that can be interchanged serve the same purpose as a cartridge?
I have an original Wurfflein muzzleloader, built in Phila around 1860, which uses the same type of hammer and firing pin as a break open single shot rifle. But it does not break open and has no hinge. The percussion cap is placed on a nipple over half way up the hollow barrel through a hole underneath and the powder and ball are placed in through the muzzle. The hammer falls on the 14 inch long firing pin, pushing it forward to slam into the cap on the nipple. the nipple is centered into the barrel in line with the bore. Center fire?