These were modified by the Danes to mount an IR night sight. The 2 mounting brackets are welded to the receiver and the big globs of weld look quite nasty.
They are still a servicable receiver. I have owned a Beretta receiver, complete with the rail that bolts to the brackets in order to mount the sight, for the past 10 yrs. I had considered sawing off the brackets and then grinding/milling off the stubs and welds to restore the receiver to it's original configuration. The idea was then to re-park. Rather than doing this, I went ahead and built a rifle on the receiver as is with the idea of possibly locating one of the Danish night sights at some point.
If the welded on brackets and weld were removed and the receiver re-parked, I think the original weld spots would still be evident because of heat variations caused in the receiver steel by welding. Other than a some purely cosmetic blemishes in the re-parkerized finish where the welds were located, the receiver would still be entirely sound and usable.