I think I may have located the production code for our original (white factory installed battery). No stickers,no imprinted nbrs. on the actual case itself, but take a look at the top of your minus post. Doesn't require removal of the cable, just reading the stamping on the exposed top of the post. My car was produced in Nov. 05 per door stamping. My minus post has two # fours on top of it with an 05 underneath, all hand stamped on it's surface. One of the 4 nbrs. has a red paint mark over it. I feel this must mean the battery was made in April 05. Probably not unusual for about 6 mths. to go by before it makes it to the finished ***'y. line to be installed. What do you think?

 

A standard manufacturing practice is to label with build week and year. So the 44 may be week 44 of '05. The red dot could be a security function after stamping.
Or you may be correct and it is April '05.

 

My original Varta battery I believe was stamped on the side top lip if I remember correctly, anyway I did see the date of manufacture and it was not on the terminal. the following is the North American method of dating batteries.
Batteries are stamped with a date code or have a sticker attached with the manufacture date, most codes start with the letter indicating the month: A for January, B for February, and so on. The digit denotes the year: 0 for 2000, say. For example, B8 stands for February 2008. A sticker on a stamped battery or a second sticker on the battery with a similar code indicates it was recharged at that date and is not the manufacturing date.