NOTE: I posted this topic in Factory Rifles, but thought I might get a better response here given the nature of the question.
I recently purchased a Marlin XT22VR that came with d/t'd scope bases on the receiver. I scrounged around and found a pair of weaver rings, mounted a 22 scope and went shooting. I noticed the gun was having problems keeping zero. I thought it might be the old rings, or the cheap 22 scope, so I ordered some Burris Zee rings and took off the old scope. I noticed the bases weren't completely secure. When I removed one, I noticed the edges weren't narrowed and both the new rings and the old rings failed to sit flat on the base, and were canted. I'm not very familiar with scope bases/mounts, so I hope someone can either identify the base type, or if this is a manufacturer's error. Some of these new Marlins are getting through QC with minor flaws. Below is a link to a picture of one of the bases. Thanks for your help.
Please note: These bases have no markings, and I have no idea what kind they are. The large, flat edges are what I find most confusing as I can't find any rings that would fit.