oil tank

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...

Do you need to be licensed to install a fuel gauge on an oil tank in Massachusetts. When I was looking online it looked like you only need to be licensed to install the tank or work on the fuel lines and safety valves. General Laws Part I Title XX Chapter 148 Section 38J I installed a Wi-Fi...