Mixed up my pods and AirPod cases – help from serial numbers?

I have two set of Apple AirPods 2nd generation, one bought in 2021 and one in 2023. I bought the new ones because it seemed the battery of the old ones didn't last as long as it used to (I am talking about the battery in the pods, not the case).

Now, I think I have mixed up the pods and the cases, putting the old pods in the new case, but I am not sure. I am trying to get help from the serial numbers, but apparently the serial numbers of the pods cannot be identified online. I have tried Apple's serial number lookup and other serial number lookups.

Also, if you stick to the info that the 4th letter in the serial number defines the year of manufacturing, all four pods are manufactured 2013 or 2023, and neither make sense.

Supposedly, the first three letters represent the place of manufacturing, the 4th the (half)year of manufacturing, and the 5th letter the week of manufacturing.

The following three letters should be unique to the device (omitted below), and the last four letters should be the model.

The serial of the old case is:

FWYC7---LX2Y

and the new case:

H16LT---LX2Y

The serial of the single pods are:

H24LT---JJNW and H24LT---JJNV

H0PLJ---JJNW and H0PLJ---JJNV

Can anyone help me find out which pods are older and which are newer?

Thanks