Could anyone price this thing for me?

Is there any general maintenance that a safe like this requires ? I’ll access like 1x every month or 2 It’s not in a high humidity space as I have a dehumidifier near by

Hi all,
I’m wondering how much you think this old safe is worth? I just picked it up for $50 and I believe it’s a Amsec BLB3018. The door is 1 in plate steel and the body is 1/2 in plate. It is certainly a “burglary” rated safe, but it does not have an official TL rating from UL. I was hoping to get $500+. I was also thinking about giving it a fresh coat of paint and I’m wondering if you think that this is worth the time/would it increase the value much. Thanks!