Other Neat Tubes

There are so many neat tubes out there.
One by one, I will add to this list as I go through my collection.

A miniature tube with a quartz crystal inside.  Used in some early color television sets. quartz crystal tube
Rather large mercury switch. mercury switch
An early 6H6 engraved metal tube with a flat top. 6H6 flat top
A tube engraved with the call letters WJAR on the base. engraved base
A Sylvania type SN4.
Thanks to generous feedback from several viewers, I now know that this tube is a neon filled strobe called a "strobotron", and may also be numbered 1D21 or 631-P1.  Following is a link to a very nice website with instructions for a project using this tube. Strobe project
Sylvania SN4
An RCA JRC927 phototube.  Only three pins on the base. RCA JRC927
A small 7 pin strobe tube used in precision timing equipment. strobe tube
A German made 7 pin phototube tube used in early automated equipment. photo tube   photo tube