As the coil rotates the contact arms pull the slider bearing assembly sideways along the slider contact bar.
Some coils have one contact assembly, others have two.
These small roller inductors are used in the multiplier tank, driver tank,
and antenna output circuits.
The roller inductor is 1.25" diameter - the slider contact arms are worn,
do not work well, slip off the coil, and need replacing.
If you have any parts like this please send me e-mail with info. Thanks, Nick K4NYW