What does M represent in model number

LuxStar wrote:

M = retail unit (new)

J = Japan region code

M is correct for the model number. But serial numbers carry NO meaning. Apple stopped using serial numbers which have any meaning a few generations ago as serial numbers are simply randomized numbers and letters. Thus J in a serial number does not mean Japan region at all.

M = retail unit (new)

J = Japan region code

• The model number of reasonably modern Apple devices start with an A, followed by 4 numbers, like A2482 (US), A2631 (CA/​MX/​JP/​SA), A2633 (Global/​rest), A2634 (China), A2635 (Russia) for the ‘regular’ models iPhone 13 for various regions but multiple country groups (differences in antennas, etc.)
• The number usually starting with M is a device order number. Somewhat related to model, but different, and includes unique packaging and documentation, like by country (e.g. printed language, sometimes accessories). M-devices were new for retail, officially refurbished devices get an F-number, replacement devices get an N-number, and personalized (engraved) devices get a P-number. The letter or letters before the slash indicate the intended market region (country or countries) (e.g. D/ for Germany and select neighboring countries, J/ for Japan).
• Serial numbers used have a bit of meaning (factory location, week of manufacturing, etc.), but not anymore for now new Apple devices. The composition of serial numbers is more randomized now, and mostly not decodable outside Apple’s own lookup services.

What are you trying to achieve?