Greetings,  The tube you received was originally installed and functioned properly in a
Dynaco MK III which was doing duty in a professional organist's system that we changed over to a solid state
rectifier in pursuit of better bass response and reliability.

There is a known arcing issue in rectifier tubes in  Dynaco tube amplifiers and is generally caused by the inate voltage overshoot at turn on
and is aggravated by the aging of  capacitors.
It is most pronounced when one power cycles the amplifier when warm.
Some  add solid state diodes to the power supply to reduce this overshoot.

If you are a purist, you will most likely want to retain the tube rectifier, however you might want to consider installing a
solid state rectifier with a time delay function (Weber copper cap) or lower the bias voltage some to mitigate  the overshoot issue.

Best Regards,
Eric