Need mold info for this 45 slug

Somebody here gave me a bunch of oddball 45 slugs. These are 240 grains and sized to .454.
For some reason my 45 Colt chambered 1873 Win LOVES these things. Like half inch group love....And of course I only have 15 left. Any ideas on which mold these came from???

They are not frosty, it is some sort of tumble lube that is one them. The weight is throwing me off as well. They are a wee bit shorter than the regular 250 grain cast bullets I usually use. I weighed 20 of them before shooting them up today and they were all between 240 and 242 grains. ( as coated)

I will goof around with one tomorrow to see how hard they are. They might be straight wheel weights. They sure shoot great in my picky Japanese made 1873 rifle with 9.2 grains of CFE Pistol and a WLP primer. They are right at 1,200 fps from the 20 inch barrel.