On the plus side, I'm pleased to see that John Birch guitars is a firm in Great Britain, removing any political aspect from the brand naming.
I had no idea about the US John Birch until I started doing Ebay searches years ago. I did wonder at one time why Bob Dylan would sing about a guitar builder!
At least this seller has done his homework about which pickup Iommi uses; though his is overpowered, even for a Magnum, and would be rejected by Tony. Apparently he's prefers them to be about 18kOhms.
I've got a copy of an i'view Tony did with a guitar mag. Lots of detail about Old Boy & history (John Birch built Tony's 1st custom SG to cater for his damaged fingers, Tony liked it so much that he financed him to build guitars rather than repairs and pickups) but in it he repeated a rumour about John Birch and Birch sued the magazine for thousands. Kinda shot himself in the foot though because the mag had very little to do with John Birch up until his death.