The tank model is MINS30T6LX13.
The serial number is BD6142865.

Is this thing a 1985 or a 2005?
It is a 30 gallon, "tall" propane with a side feed cold inlet and a top exit for the hot.

It was in my boyfriend's mobile home when he bought it, but we took it out and replaced it with an electric hot water tank. We think that the propane water heater was leaking raw propane at the control valve.

The mobile was a 1987 year model, but it was placed on its own land plot in the early 2000's. The mobile was vacant for 3 years before he bought it in 2010.

Could a 1985 hot water tank last 25 years, considering it may have had at least 5 years of drained non-use?

Damm that company for not just being normal and stamping a normal month/date manufacture number.