[Tim]

I used to have one of those, when I was a lad( well 20 any way)an earlier all silver one, “aquired” from one of the college throw outs. This might have had a +/- 9 volt supply derived from 2 PP9s. I also remember making a mains supply for it, as batteries were expensive even then and ( due to my ADHD) was worried I might forget to switch it off.
I found the frequency was surprisingly accurate when measured with a borrowed frequency counter. I too seem to remember the arrangement with the meter pointer.