How do I report the sale of a gifted item on federal taxes? We received an old rifle (not sure antique?) from a family member as a gift, and sold it within a year.

We leant the relative some money, and received the gun as a gift. I'm not sure if this changes anything. I believe the gun was inherited by the gifting family member years ago. How do we go about reporting this on taxes? We did not have the gun appraised, and I'm unsure as to the cost basis/fair market value of the gun.