I'm sure you know, which is why you showed it, but the first proof mark in the first post with E G and a Star is missing most of the L, which would be the proof mark for Liege, Belgium. Fascinating city with its firearms history.
Show us the photos of when you shoot it!
@Frontier's, I am going to suggest that you get out your calipers and measure the bore. I am thinking that the 16.0 is the bore diameter, but in millimeters. That translates to 0.630" which brings your new (to you) smoothbore back to being a 20 gauge. Get some calipers before ordering any 16 gauge components.