Possible AirPod's MAC address: 40: DF :29:8E:AC:C1
MAC addresses are divided in 2 pieces, each piece contains 3 groups.
40 : DF : 29 = VENDOR
8E:AC:C1 = DEVICE ID (unique ID of the hardware used)
Usually Apple had VENDOR: 70:70:0d
But as these are HEX and accept only values "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F" they need to change the VENDOR ID at each batch of new devices basically.