Some background knowledge on the eneloop coding.
The numbers 1, 2, 3 and 4, as in HR-3UTG /BK-3MCC /BK-4HCD are simply stating the size of batteries. These numbers are used on all batteries in Japan.
- 1 stands for: D
- 2 stands for: C
- 3 stands for: AA
- 4 stands for: AAA
単三 : Tan-San (san means three) which is the 3rd size. But we call these AA.
単四 : Tan-Yon (yon means four) which is the 4th size. In the western world we call them AAA.
Take note that some foreigners get confused while shopping for batteries in Japan because of a mixup between size 3 = AA and size 4 = AAA.
Reading the manufacturing date:
On the side of every original eneloop battery you can find a date code embossed. You can decipher it. (if yours doesn't have any, yours are likely fake)
The embossed code doesn't have any color, so you need to look up real close
For example the following code: 16-08 xx
the first 2 numbers indicate the year: 16=2016
the next 2 numbers indicate the month: 08=August
So this battery is a 4th generation Panasonic eneloop battery produced in August 2016.