This is a new CTR Engineering TPS3 suppressor for AL811H amplifiers. It fits three-tube 811 and 572B amplifiers. I designed the original AL811 amplifiers and dozens of others.
The original tuned suppressor was supposed to use 5-turns wound on a .375″ rod, spread to hole distances. There was also supposed to be a thick washer under the board to prevent shorting the 100pF resistor resonating capacitors near the choke.
The resistor is a known internal inductance that resonates with the capacitors, it is not non-inductive.
This suppressor was developed when non-inductive resistors were unavailable. This type of suppressor has superior performance to other more standard types.
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See this link for the operation of suppressors:
https://www.w8ji.com/vhf_stability.htm
The CTR Engineering TPS3 for 811 amplifiers are vastly improved layouts that reduce the chances of shorts from incorrect hardware. These boards provide more reliable parasitic suppression and are less critical for mounting.
This system is vastly superior to hairpins and has a much better layout than the OEM Ameritron parasitic board. The TPS3/TPS4 system has a faster resistance slope with increasing frequency, and more suppressor series equivalent resistance at 811 problem frequencies that occur just below the FM broadcast band and around 225MHz.