From: Al Kossow
is it roytron/Roytron500_1966.pdf ?
That sure looks like it! The illustration on pg 5-16 of the DEC PC054/PC05
manual looks just like the thing illustated on the cover of that.
I wonder why it didn't turn up in the Web searches? Probably because this
doesn't include the term 'maintenance manual'?
I'll add the link to the article.
Thanks!
Noel