Please help identifying the part. What is it? Thank you.

Looks like a spark gap, typically found in a telephone socket.

Spark gap could from a CRT monitor or TV set.

This picture is not the same kind but you can see what is happening inside.

https://www.epcos.com/blob/174146/download/5/ueberspannungsableiter-und-schaltfunkenstrecken.pdf
If that link works you can see a TDK catalog of SURGE ARRESTERS AND SWITCHING SPARK GAPS.

Picture of some spark gaps (surge arresters).

Definitely a spark gap. Typically used for protection, but can be used in HV oscillators. I've replaced a few.

Funnily enough another well know Forum covered this recently..

The pictures posted above are those of "controlled" spark gaps. Manufactured to arc at a specific voltage overload more or less.....cost money...

Poor mans or "once off" spark gaps are normally designed into a PCB.....they have teeth and are part of the board design..

Cost nothing but really work when they have too...like is there is serious dwang coming along and they help to quench the extra voltage/energy and arc over.

If they handle it maybe once in their lifetime.....they have still done their job. At no extra cost.

LOL....thinking back now...the old Telefunken 711 had a glass spark gap protecting the tube from excessive G2 on the tube base board...we had hassles of note with them...so we simply cut them out...way overdesisgn from Telefunken at the time....it's not like too much G2 can neck a tube

Regards,
tvtech

Thank you All. The pdf above is very educational. Tvtech, please could you give a link to the discussion on "another well know Forum" ?