I have been searching my files for a copy of the ads, but may not have them since it predates my keeping of almost everything even remotely connected to ammunition in my files, but I cannot remember the importer. I want to say Century Arms. Whichever company it was imported a huge amount of this ammunition into the United States perhaps 20 years ago, or more, and they had purchased it believing it was 7 x 57mm Mauser. Of course, they quickly found that there probably weren’t three firearms for this caliber in the entire United States, and they began selling it cheaply. At one point, they put box ads out indicating they had a quantity for sale open to offers to purchase. I think that is when the various little firms that bread down ammo for components got into it. AKMS is correct - it used to be sold at gun shows for whatever anyone could get for it. Guys thought they had a rarity, and found that at shows in any given region, after they sold a few boxes, they had saturated the market for that area, and before long, you could buy this stuff not just for a buck a round, but for little over a buck a box. I bought one box and I had the cartridges and box for almost ten years before the last round was gone and I gave away the box with the last round.
If anyone has any of the early ads for it, or can even tell me which firm imported it, I will appreciate it. It would have probably only been Century Arms (pre-Florida days), Service Armament/Navy Arms or Interarms. I really think it was Century, but just don’t positively recall.
I still think of it as a common cartridge among collectors, with a very low cash value, at least in the variations that came out of Venezuela into the U.S.