[GarySP]

Thanks for the information, Arran.  I did not know the 80 tube was built in a GT casing.  I've always seen globe or ST only.  I agree with you after taking a closer look; those look to be original tube socket rivets.  Steve, if you don't have it you will want to locate a tube shield.  They pop up from time to time on Ebay, and I don't recall where I saw it but there is someone out there that makes reproductions.  A little patience and some sheet metal and you could probably fabricate a working version yourself.  Original-style speaker cloth will be a bit more of a challenge to locate.  Take care, Gary