What is this thing on a deaerator?

I was on a job site last week where we got convinced to supply a deaerator, which is not normally part of our scope.  So, I have very little knowledge of deaerators and their valve requirements and such.

Anyway, the company in charge of doing all the piping has installed this thing (see attached) on our DA and I have no idea what it is.  Can someone tell me what it is and what its purpose is?
the last item on the line going into the valve on the end nearest the
picture taker looks like a check valve, so I'd support the chemical
injection point.
Definitely not a hot tap by any definition of hot tap that I've ever
used. Though I have seen hot taps on vessels before, this just doesn't
look like one nor does the description in the OP give any indication
that it was installed on the run.
Having worked for RCS for 17 years, this is definitely not a corrosion
coupon "retractable" holder.  Looking at the end, it appears this might
be a check valve.  If it is, this is for injection purposes.  If you
look into the end and see pins for an electrical connection, then this
is a corrosion probe, though not likely.  Usually, chemical injection
quills have valves at the end to shut off the system and isolate it
while not being used.  This was inserted and fixed so it is not
retractable, but adjustable is more like it.
From the originalGate Valve
.