I recently became the proud owner of a 1983 Biacrown era Hiwatt custom 50 head. I have a small issue that is plaguing me though... The plastic plate that identifies what ohm you are selected to was broken off. The last owner replaced it with a piece of paper that has only 8 and 16 ohms. I was wondering if my head had the possibility for 4 ohms like all other hiwatts i've seen? If so, are the 4, 8, and 16 positions in the exact same place as say, this head?