Send it to me. I would keep it dry in my shop and lovingly wipe it down with Ballistol every couple of days.

Talked with Frosty, he said wire brush I used 4in wire wheel an a couple coats boiled linseed oil an 2years later no rust,an my anvil sits under a open lean 2 off my garage !!

 

The reason I looked up a clear paint is because at some point someone is going to question your statement (or memory) that it is a insert brand here anvil and marked x -x -x in size, serial number xxxx.  Paint would have to be removed to prove the information. Clear paint would have the information so it could be seen.