Depends what you mean by "Legal." Legal is multi-dimensional: Own, Sell, Carry Open, Carry Concealed.
Now, the Benchmade AFO is indeed a switchblade. You press a switch, blade opens automatically via spring tension. A common misconception is that switchblades are illegal to even own everywhere in the US. This is false. Federal law only controls the sale and importation. The rest is left to the states.
By PA's law, restrictions are a bit tight. You are legally allowed to keep one "solely as a curio" (meaning for collection purposes privately in your home) but you cannot carry it anywhere, concealed or openly.
With the legal matter out of the way, I would like to ask where/how you got it? I have had my eye on the BM Bedlam, it is a gorgeous piece. But I don't know how to get one and in my state of MD, we can own them and open-carry them, but they cannot be sold.