Based on
this, you have a matching numbers Steyr STG-58 kit rifle, which is a top tier metric version. The Imbel receiver is top tier also, made in Brazil on Herstal FAL licensed tooling. Forged, not cast.
Those kits were mostly torn down from pristine rifles which stayed in Austrian armories rather than being carried.
Purists may turn up their nose at the paint job, but it doesn't detract from the value much. The locking shoulder isn't peened over like some ham fisted home builders have done, so that's a good sign.
That rifle on the FAL Files would be priced at least $1400-$1500, which is a fair price IMO.
The last matching number STG kit I twisted up on a Coonan receiver and then later sold, went for
$1150 $1050 in 2012. From what I've seen prices have not come down.
ETA: The hand guards are not original. The butt stock appears to be original. A lot of US made plastic hand guards have made there way onto FALs to meet 922r US made parts count. The originals were stamped steel. The STG had a couple fine features other countries didn't adopt- the folding bipod and the slotted Stoll muzzle brake, intended for wire cutting use.
There are hardly no complete rifles in the FAL Files marketplace anymore because the salad days of FAL building are long gone. Hence the premium prices when one is listed.
ETA: Checked some paperwork and found correct price of rifle sold in 2012.