Hole in oil hot water heater

[newhomeguy11]

I recently replaced my 2 year old 50 gallon oil hot water heater (switched over to gas). I told the installers to leave my hot water heater since it's almost brand new and I figured I could sell it. When looking at it today, I noticed a strange hole in the side (see pictures). Does anyone know what this is? Not sure if it's always been there, or if it's something the installers damaged when replacing it. Any help would be appreciated. Thanks!

 

[Geofd]

sorry it's tough to see my computer is down and I'm using
an iPod to see pics is it a threaded connection????

 

[newhomeguy11]

sorry it's tough to see my computer is down and I'm using
an iPod to see pics is it a threaded connection????

It's definitely a threaded hole, about the size of a small screw.

 

[Jeff Handy]

Pbly just a hole to mount an accessory if needed.
But don’t know, just guessing.

 

[FishScreener]

A mount for the seismic restraint?

 

[Jeff Handy]

Maybe a nanny cam, haha?

 

[Diehard]

Do you have the owners manual to see if it is shown and/or mentioned?
Otherwise, ask the manufacturer.
Does it have a bottom to the hole or can you see insulation in there?

EDIT: That hole was definitely fabricated in the tanks shell, when made. Not something the plumber did.

 

[TomFOhio]

If you didn't have water squirting out of it then its probably something for shipping the tank when new. If you stick
something skinny in the hole does it stop at the tank.