Barrel perforations
Perforated for electrolyte cross-flow.
The perf holes were made with a 1/8" soldering iron tip. At the time, it seemed easier and quicker than trying to drill them.
Burning the holes left a nice smooth raised "donut" on both the inner and outer circumference of each hole. These (I thought) would be beneficial to tumbling action.
Well, they were TOO effective. Parts would hang up on these donuts so well, that they were carried all the way 'round, instead of tumbling!
Spent a lot of time carefully cutting all the inner donuts away with an xacto knife! So in the long run, it would have been better to drill them.