Mitsubishi Electric Mr.SLIM PLA-SM EA Série Manuel D'utilisation page 175

■ The serial number is indicated on the SPEC NAME PLATE.
Sequential number for each unit: 00001–99999
Month of manufacture: A (1), B (2), C (3), D (4), E (5), F (6), G (7), H (8), J (9), K (10), L (11), M (12)
Year of manufacture (western calendar) : 2014 → 4, 2015 → 5