Its all in the screenshot. A low level weapon requiring lvl 6, with a t2 flat fire mod… listing +16 flat fire.
I believe ive also come across a +11 fire one, then upgraded it to t3, it remained 11 (or became 11 while it was a graphical bug before? dont know), but that one was many hours ago sorry.
In any case, it was +flat melee fire damage in both cases
edit : upgraded the one on screenshot to “tier 3” for a nice +25 flat fire damage… ^^"