I attended the Unmanned Systems 2015 conference and tradeshow hosted by the AUVSI May 4-7th at the Georgia World Congress Center in Atlanta, Georgia. My presentation, Advanced Power System Selection & Maximizing Efficiency in Multirotors, was well received by the thousands of attendees at the conference. Click on the link in the previous sentence to view the .pdf copy of my presentation.
Here is how you decode the part number on a Cobra motor.
The last motor you listed below has the following part number: CB1501133193
The part number is broken up to the following groups: CB 15 01 13 3193
CB = Cobra Motor
15 = Made in the year 2015
01 = Made in January
13 = Made on the 13th day of the month
3193 = Serial number 3193 from this production run
The number is laser engraved on each motor after it is manufactured at the factory. If you are looking on a website, you cannot go by the serial number shown in the photo, because that could be any motor, and the serial number may have been PhotoShopped onto the photo.
On the box itself is also a date as shown in the photo below. In the lower left corner you see the date 01.04.2015, this date code would be read the 1st day of April, 2015, which is the date the motor was packaged. Normally this is the same date the motor was made, but it may be a day or two later on a very large production run.