Special NMI Super Nintendo & 1Chip Comparison 

The engraved number in the bottom sticker most likely means the year 91, and the week number 34. Meaning sometime during the third week of August 1991. Why the early models and later models didn't have them engraved is beyond me. The other nice thing about the 1chips is they are more reliable compared to the 3 chip or "2 chip" models as everyone calls them.