The Ruger SR-22 is a 10/22 receiver inside of the Nordic outer covering.  
The Ruger receiver serial number is visible on the receiver due to a small window that is machined in the Nordic receiver cover.

If SBR'd,  and never changed from it's current configuration,  can the cover,  which is affixed to the receiver,  bethe  engraved part?

Or would a person be forced to have another window milled in the Nordic cover, in order to see the engraving on the receiver?

Or another possibility....can the receiver be engraved with the SBR info,  but then covered,  
which would mean in order to see the SBR engraving, the cover would need to be removed?

Thoughts and alternative methods welcomed.

Reciver or barrel "unless they changed that", I put mine just behind the ejection port. It also has to be visible from what I understand to just milling a slot would be needed.