[jr_tech]

Originally Posted by old_tv_nut

This treatise
http://www.earlytelevision.org/damper.html
indicates that the grids were used to effect a a linearity adjustment.

Interesting reading! I also looked up several of the sets mentioned above and indeed see the grids in a linearly adjustment circuit... I have never encountered a set with this linearity control configuration. Thanks for posting!

jr