Can Somebody identify this waveguide

I've got a picture of this waveguide. Can somebody can tell me what type of waveguide is this. Picture is attached
I would be very thankful for the help

Sorry, the picture does not show any good scale.
The photograph does not show the waveguide but this looks like a pressure window.

Please try to measure the rectangular pattern in inches, then you can find the WR-XXX waveguide format. If the coaxial connector barely visible behind the flange is BNC, the waveguide can be for C-band or max. 5 GHz.
You can also measure the outer dimensions of the waveguide and look into tables of standard waveguide sizes.

This looks like a "receiver protector", which may have a gas tube behind the slits where the white windows are. If it is, don't screw with it, it might have radioactive gas inside.

It is obviously not an ordinary piece of waveguide, which would have a big rectangular or circular hole.

Biff44 thanks alot for the help. Can you please tell me what type of input is this. Is it a dual cavity?
It is a receiver protector.There are two slots as the input to the waveguide. What is the white material in the slots. is it some dielectric. Or some protection?

the white stuff can either be plastic or ceramic. If it is ceramic, the cavity behind it is probably filled with gas. If it is plastic, there is probably a glass cylinder on the other side filled with gas.

The concept is pretty simple. Like a neon light bulb with voltage across it, if you apply enough RF voltage to the gas cylinder, it "turns on". When it "turns on" it looks like an RF short circuit and reflects all energy. It can handle a lot of power, like 10 killowatts.

Thanks alot