The thread on the BGS Forum started with a post of an instrument just like India Four Two's, which I derided as being a spoof. (It was, in fact, the clock shown in India 4 2's post) Bill Chivers then directed me to a Youtube video -
YouTube - Chuck Yeager Making New Records. The title is Chuck Yeager Making New Records. There are several shots of an altimeter reading 0 to 12 in one revolution. So I have apologised and admitted that this type of altimeter does exist, but I don't like having a partial picture and would like to know the full story.
Dick