The way recommended levels work, what you lose is a percentage based on the stat, and how close you are to the level. Usually, AC and HP/mana are the ones that reach full stats last, with resists and regular stats topping off first. Since the AC is so low, and this item has no HP/mana to begin with, it's no surprise that this reaches full stats below the recommended level.
btw, I'm not sure *exactly* how the percentages work for recommended levels, and whether they follow a curve the higher the recommended level (as in, if an item as a rec of 10 and you're level 8, there's a much bigger difference than if the rec is 50 and you're 48 - the percentage difference is much greater), or if it's linear the entire way up. This is just from personal experience.
Yeah I just got this the other night and I'm lvl 51 and there isn't decrease in stats, at all. What I've seen is that when you are really close the recomended lvl mana and hps are hurt the most and ac/stats/resists aren't touched with only a few lvls in there.
Thats only a recommended level. You can use it below 53 but it will have less stats then what is listed, and they get lower the farther away you are from the recomended level. If you used it at 52 I would guess you would lose a point in just one or two of the stats listed there. I use a bow that is recomended level of 61 and only lose one point of mana at level 60.