Amperex 6DJ8 tube construction

This is just a guess, but a splatter shield may be to prevent secondary emissions.

Brent Jessee -from Audio Tubes - was kind enough to explain.

The splatter shield prevented getter flash material from migrating down during the flashing process. Without the shield the flash material could stain the grid and/or plates and affect the operation of the tube. The shield has no effect on the sound and like the o getter is pretty much useless after the getter flash process is complete.

I can add a bit to that. The getter is used to trap all remaining air molecules in the aluminum of the getter. After all the air is pumped out and the glass sealed, the getter is fired with a very high voltage. The air is thus trapped in an aluminum deposit seen on the inside of the glass near the getter. Because its aluminum, if the glass seal is lost, the getter deposit turns white with aluminum oxide in a matter of minutes.

The getter can be ’over-fired’. If this happens other elements in the tube can be contaminated. That splatter shield takes care of that (I wish they were used in Chinese tubes, which are often over-fired..). As Amperex improved their technique, the splatter shield wasn’t needed. Getting rid of it is a good thing, since it can contribute to microphonics.