Sale of an inherited object

I found an object while cleaning our my deceased parents home that I imagine would be considered an inheritance.

I subsequently sold the object through a 3rd party auction house on a lark (parents had no idea of it's value). 

I received  an amount more than expected ( >600.00$).

The auction house will be sending me a 1099x and will be reporting it to the IRS.

Is this money considered reportable Income or just considered part of  my inheritance?