Thank you, TVP. I appreciate your expertise.
I have contacted our vendor. (What I should have done in the first place.) He informed me that our part was too large to be half hard and parts this size are 'as cast'. How much does the material properties of brass vary in the 'as cast' state? The info I've gathered isn't too promising; the yield strength for C36000 can vary between 124 and 340 Mpa.