Damaged EGR valve?

[Ignazzz]

Hi all!

Seeking for some help here related to EGR valve. I have recently bought a 2006 A6 with a faulty throttle body. As I was already removing the throttle body and was close to EGR valve, I decided to clean that as well. However, as I started to clean it, I have noticed an odd metal ring (seal?) fitment there:

I have managed to put the ring back into the grove of valve but it seems that the ring pops out again after a few turns of the valve shaft.
Is it just me putting the ring back wrong, or maybe there is a certain point for the ring seal gap to be aligned (as of now the gap is on the top)? Would this in general mean that this EGR valve is not usable at all?

 

[NHN]

Is that stock valve or modified as not seen that design tbh, looks like a dodgy egr delete lol.

 

[Ignazzz]

Is that stock valve or modified as not seen that design tbh, looks like a dodgy egr delete lol.

Seems to be stock while comparing visually to the ones I find online (of course there is a chance that previous owner installed some random Chinese valve lol). Thought, that shaft weld looks weird to me too...
Is there a decent way to check if EGR has been deleted by the previous owner?