PW5 Purchase of Paperwhite 5 below 5.16.3 (identification by serial number)

[rados2000]

Sorry if I wrote in the wrong section, this is my first post on the forum. I would like to buy a Paperwhite 2021, but I'm having trouble getting the correct version for JB without opening the box.

The production date can be found from the serial number, which consists of 16 digits. The third group of 4 digits will determine the year of production, week and day of the week. Version 5.16.3 is stated to be released by Amazon in July 2023. However, the firmware file appeared only on August 30. Therefore, it is not clear which week is the boundary. Maybe in July devices with version 5.16.3 were already arriving from the Amazon store, and the firmware file was posted by Amazon later?

And another very important question, with what firmware and production date are Paperwhite 5 now coming from the Amazon store? Is there any chance of getting devices with a version lower than 5.16.3?