Rare tektronix type P plug-in test unit!!!

Description

Here is a rare Tektronix Type P plugin!!!
Among the dozens of plugins I've seen there has been only one of this!!!
The P is used to test 500 series Tek scopes, their risetime, and to align the delay line.   Without it it is difficult to get a Tek scope back to factory specs.  All those dozens of piston capacitors on the delay lines?  From my experience they usually need some tweaking to get the best rise time and flatness.
This plug in gets its very fast risetime by using a custom mercury relay.  Semiconductors were not fast enough-- it takes an actual high-performance switch to get the very fast rise times needed.
This particular one has been plugged into a type 556 scope and seems to work perfectly.
Buy this now!!!   They are a godsend if you want to really tune up a Tek 500 series scope!!