Jake,
the RBL forgings are machined in the heat treated condition. They are thru hardened 4140 if memory serves and should be in the mid 30's RC. They will file well enough in the hardened condition, albeit take longer than an annealed steel. Tony said this was done to assure precision fit of the parts. Personally, I wouldn't anneal one to prep it. Whether or not an engraver would need it annealed or softened is something I don't have any experience with.