I found a safe during a tenant move out. Tenant has no idea.

So I was doing a move out walk-through with a tenant and saw a big box on a shelf in the laundry room. I asked him about it. He said he had no idea what it was and that it was there when he moved in in 2009. Felt pretty heavy. I spun it around a bit and saw that it's a First Alert fire safe with a standard rotating dial, about 18" cubed. The property has turned over twice since the tenant moved in so tracking down who it belongs to is likely a chore. I can see the serial number so I could check with First Alert to see if it's registered. Other than that, not sure what to do. Any advice? Thanks.