M4 stamps different than others

[November45]

Hello everyone, I have looked at many forms but the way the search engine algorithm works, I can't find my answers.. I've seen on many m4 stamps that they are magnum Tested ( two star ) but mine only has the one star.. did I mess up buying a new model? And should I try to find an old used m4 with more stamps. I've seen some with 4 stamps on receiver, and I only have 2, the CIP S and the single star over whatever the other symbol is. I will try to link a photo. Thanks for the help, I'm just confused at why some are magnum rated and other not.

[Plinkingaway]

I searched high and low and found nothing on this. You might have to contact Benelli directly. 
 

If you do, I for one would be interested in what you learn. 

[Plinkingaway]

After more research this is what I found out: 

As far as I can tell the CIP S refers to the 1370 bar burst test that the firearm was subject to.  The marking to the left is hard for me to make out, but I think it is the proof mark for steel shot, though I could be wrong. 
 

In any case, I’m pretty the 1370 bar test is what clears it for magnum shells. 

[blfuller]

It is the mark of the Gardone proof house that does the Benelli proof firings.