I have a chinese mag I bought recently, that's a little different than my other flatbacks, I might have had one before and just not noticed. On all my other mags, the little hump that runs up the spine, stops right before where the mag catch is welded on. On this one, it runs up under the mag catch, and the mag catch has had a little channel milled in it. Wondering if this is just another chinese variant/change in tooling or manufacturing method etc. Pic, mag in question is on the left: