if you hit it and it rings it's harder than WW alloy. Probably linotype or close to it.
I'd really not worry about the exact hardness.
I'd look to trade it to someone for pure lead for a 1 lb to 1 lb ratio. Probably just each pay shipping and you'll be good to go.
Whatever you are willing to put up with, is exactly what you will have.
When your ship comes in. ... make sure you are willing to unload it.