Strange grid resistor arrangement

[Guest]

I am finishing the restoration of my (69?) plexi. It had the look of a sloppy 80's hair-band mod job. Instead of feeding the power tube control grids through parallel 56K's, it goes straight to the grids (from the 220K bias/.022 signal junction) of the interior tubes, then thru a 15K resistor to the grids of the exterior tubes. What the heck is this? These resistors are tan-colored but cylindrical (early carbon film or later carbon comp? that's a question) and the leads are sheathed in that old style cloth/chinese finger puzzle stuff. Anyone heard of this 'mod'?