That's the stock EMG BTC (bass-treble control) knob. I bought that bass new, and I was told it was a 'deluxe', maybe they just called it that because it had the EMG's. List was about $2300 (per the store tag), -no kidding, and it had been 'on sale' (street priced) for $1699 for a long time before I bought it. Mine is quite a bit lighter than the few others I've played. I called Bassnw and they got me a white pickguard for just under $50 shipped, but that was a few years ago now.