I don’t understand how this light can perform so well…

According to this SK68 comes with 17.7 mm lens (the convex part only).

I took the Enderman’s calculator, entered:

- 92% glass transmission (about what is expected for uncoated lens)
- Clear Aperture of 1 (a perfect lens which this is clearly not)
- 17.7 mm diameter
- 172 cd/mm² surface luminosity

I got the 39 kcd that you did. But….

- I assumed a perfect lens - according to these calculations you’d need more than 172 cd/mm² to get 39 kcd.
- According to sma dedomed XP-E2 Torch maxes out at 141 cd/mm² and does 138.6 at 2.2A.

So… 29 kcd would already be very high according to these calculations.

Does anyone have an idea what’s going on?

Maybe the calculations are wrong?

Maybe your SK68 has a bit larger lens?

Maybe the lux meter that you used 6 years ago significantly overread the output?

Maybe it’s an editorial mistake you actually measured 29 kcd?