Updated: I managed to unlock the physical damage requirement by having it in the secondary weapon slot.

This arc rifle rolled 2 modifiers relating to poison damage, and the item picture and model are for a radium carbine.

Name and skills are correct for an Arc Rifle, but everything else appears to be for a Radium Carbine.

Original below:

Ancient Relic Item:

Arc Rifle which deals Heat(Electric) damage.

One of the unlocks requires dealing 50,000 points of Physical damage.

Construct damage doesn't count.

How exactly am I supposed to unlock this, when it's the wrong damage type?