This is an HKS "Competition Box" that I could best describe as being a speedloader for your speedloaders. Basically, this will hold 60 rounds of ammo pre-arranged so that you can set a speedloader down on it and pick up the cartridges directly.
This one one is #60P, and says that it will work with speedloaders 586-A, PYA, and M3-A. Basically, it will work with a 6 shot 38/357 medium-large frame revolver such as an S&W L frame, Colt E/I frame, and I think the Ruger GP-100.
Even though it was made by HKS, it should work with speedloaders of any make that are designed to work with these guns.
I stupidly bought this without reading the label, and had in my head that it was for #10 speedloaders.
I'd like $20+shipping, but am open to offers.
First "I'll take it" with follow up PM get it.