I noticed that two of my G19 magazines are not like the others. Magazines #1 and #2 are identical. Magazines #3 and #4 are identical. All mags have a metal lining. There are three differences that I can see: The metal plate (see "B" arrow) on mag #3. The dimple (see "A" arrow). The final difference is that the cutout for the mag catch (proper term?) does not wrap as far around the mag on mag #2 vs mag #3. My questions are: Are Mags #1/#2 genuine Glock factory mags? What generation are these mags? what does the metal plate do?