I can’t comment on the quality. I have never shot much of this, if any, and we never sold this brand in our store that I can recall,which means I cannot supply any customer feedback. So, I have no personal knowledge, pro or con, considering its quality in that regard.
Visual quality of the specimens I have is average, and I mean average; not poor and not sparkling perfect examples of the ammunition makers’ art. I have never encountered an outright, visually-defective A-MERC Cartridge, but do not doubt they have been seen. In 65 years of shooting, 57 years of cartridge collection, and 36 years of working in a very fine gun shop, I have found defective rounds - the most common defect was upside-down primers, but not limited to that (once found a bullet seated backwards). They are not common in any brand, but found occasionally in most all brands.
I will admit that three rounds in one box is beyond simply an occasional “miss” by the inspector. Pretty unforgivable in my view.
I have only seven samples of A-MERC boxes, one .32 Auto and six different 9 mm Luger. I have scanned all but one of the 9 mm, different only in bullet weight and zero differences in the top label, and have posted them below for anyone interested. The second picture is not over-cropped by me. The boxes are so large in total dimensions that the top of the upper box was slightly cut off by the scanner, as was the bottom of the lowest box. It does not affect anything important missing from the picture.
Note that one box is from RSR, a large American Sporting Jobber (whole-sale business rather than a retail store). At the very bottom of the label it is stated "Manufactured by American Ammunition, Miami, Florida, 33147. Visual quality of the ammunition is satisfactory. I did not bother to open, first because of the unusual Jobber labeling, but also for lack of anything to do with the very-common headstamps, which are all the standard A-MERC marking (all well-stamped, by the way.)
Edited to correct a spelling error only.