NOTE: I repeat measurements so there will several corrections as I gather more data.
Specs
Driver & UI: Boost, 12 groups for M21B, side switch UI for M21F and M21E
Temperature protection management inside (Factory set at 55° C.)
Low voltage warning: Yes (The light flashes when battery is low.)
Lens type: AR-coated glass with green reflection (the good type that drops Duv about 20 points)
Reflector: orange peel
Mode memory: Yes
Measurements from Simon:
GT-FC40 4500k
CCT 4521k
Ra 93.2
R9 76
R12 70
Duv +0.00215
GT-FC40 5500k
CCT 5598
Ra 93.6
R9 78
R12 73
Duv –0.00007
Good Measurements from Zero Air Report FC40 4500k in Convoy L6 HERE
CCT~4500
Level 4 Ra=93 R9=76 Duv 0.0016
Level 1 Ra=95 R9=98 Duv 0.0001
Measurements by me and my Opple Lightmaster Pro :+1: 
No change in Duv noted with time (heat).
Lower intensity drops Duv 30 point: Convoy M21B 1% –0.0082, 35% –0.0050
M21B 4500k
CCT 4579 Ra 98.7
x 0.3560 y 0.3466 Duv: –0.0068 (2nd measurement –0.0046)
Throw 262 m
Flux 2250 lm
M21F 4500k
CCT 4481 Ra 98.4
x 0.3591 y 0.3491 Duv Turbo -0.0030 cold, -0.0040 hot
Throw 276 m
Flux 2150 lm
M21F 4500k (visibly very magenta center)
CCT 4370 Ra 97.9
x 0.3595 y 0.3339 Duv Turbo: -0.0090 turn-on, -0.0100 hot
Throw 273 m
Flux 2220 lm
M21E 4500k
CCT 4395 Ra 98.2
x 0.3623 y 0.3520 Duv Turbo: –0.0030 cold, -0.0040 hot
Throw 324 m
Flux 2140 lm
M21E 4500k Purchased 9/2024. Looks very green.
CCT 4038 Ra 91.8
Duv Turbo: POSITIVE 0.0020
M21E w/ Getian GT-FC40 5500k
CCT ~5300 Ra 98
Duv first turn on (cold): low brightness –0.0004, high brightness 0.0004 (second measurement 0.0004)
Duv after 30 min (hot): low brightness –0.0018, high brightness –0.0007
Throw 332 m
Flux 2220 lm