Someone is advertising a NOS 3KP4 on eBay in its original Raytheon packaging but if you look at the pictures of the tube, it's an old RCA 3KP4 that just might have been what the old time owner of the Pilot-37 may have pulled out of the TV and replaced.

https://www.ebay.com/itm/314424157834

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Condition:
Used so how can it be NOS?

Maybe he means the box!!! Hey, I almost grabbed this without looking closely thinking it might disappear in minutes. A NOS 3KP4 is gold! When I looked at the metal, turned blue from heat, I thought something wasn't right. Then I saw the half worn off RCA on the pin socket. I contacted the guy last night by eBay messaging telling him his advertising was deceptive but he hasn't changed anything.

He just changed it to "Used RCA"

I just looked at the eBay ad. The fourth picture from the top looks like a 7" electrostatic CRT or a 3KP4 which needs to go on a diet!