Fitting Identification

I am in the process of trying to understand my cabin well/pump system. This system was installed in 1989.

Attached is a picture of the piping arrangement at my cabin well house. I am trying to identify the brass in-line fitting the pressure switch (PumpTrol) is attached to. What is it?

From what I can see it is a check valve that was designed to have a snifter valve installed in the side port. With a bladder tank, there is no need for a snifter valve, so the installer put the pressure switch there.

Ja, a checkvalve with a side port. A tank Tee would have been preferable.

Thanks so much for the info. The thought entered my mind that it might be some type of a check valve. I had just never seen one with ports on it with a pressure switch attached. There is also a plugged port on the back side as you can see in this picture. I learn something new almost every day, I had to google snifter valve to see what one was, LOL. Thanks again. There is another check valve on the submersible pump, correct?

Ja, there would be a checkvalve in the pump. Depending on the height of the water table, if the lower checkvalve doesn't hold, the water column falls creating a near vacuum in the top of the pipe. When the pump starts, the column of water slams the topside checkvalve at full speed creating water hammer. A checkvalve holds better if it has pressure against it so the top checkvalve is more likely to hold than the lower one in that scenario.