[ Philip Jamison wrote in 150608 MMDigest:

> There are four square bolt heads visible which would seem to
> do this, but the countersunk access holes in the case are too
> small to fit a socket.

Hello Phillip.  I have never seen a Hupfeld Phonola Vorsetzer, but
I do know that sockets for square-head bolts are common in both SAE
and metric sizes.  You don't say how big the square head is, but
I've seen square-head sockets from about 1/4" to over two inches.
It shouldn't be too difficult to find!

Bob Loesch
Northern California, USA