{Collins} Debris in 811A tubes

Hello all,
Recently picked up a 30L-1 from a ham flea market in very sad shape but the
price was great.  It was kept uncovered in an attic for many years.

In the process of refurbishing with general cleaning and installing new caps
plus diode board, I found some strange things floating around in one of the
They are black  particles that seems to have come from the plate coating,
there is a shiny spot on the plate about a 1/2 inch.

My question is can I still use this tube, or am I courting disaster?
It checks good on my TV-7D/U tube tester.
Also how good is my tube checker supplying only a couple hundred volts for
an 811A that works at 1800 volts plate voltage?

Thanks for any advice,

Al   K2DYH

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