Mitsubishi Electric Mr.SLIM PKA-MLA2 Serie Manuel D'utilisation page 178

■ The serial number is indicated on the SPEC NAME PLATE.
M
Sequential number for each unit: 00001–99999
M (indoor unit)
Month of manufacture: 1, 2, 3, 4, 5, 6, 7, 8, 9, X (10), Y (11), Z (12)
Year of manufacture (western calendar): 2020 → 0, 2021 → 1
This product is made in Thailand.