There has been some discussion recently on a range of flash guns from the Far East which appear to be clones of popular high-end speedlights from major camera manufacturers, costing but a fraction of the real things.
I decided to take a risk and obtain one of these, a "Chinese copy" of the top-end Nikon SB910 - the Meike MK910. (Not very subtle model naming!)

This gallery shows a few examples of shots taken one dreary afternoon (we have lots of these in the UK!), mostly comparing the MK910 with my Nikon SB800 (I don't have an SB910, so couldn't do a direct comparison).

The Meike MK910 has a reported guide number of 42, and zooms from 18mm to 180mm focal length. (A fold-out adapter can broaden this to 14mm.)
The Nikon SB800 has a reported guide number of 38 (so is marginally less powerful), and zooms from 24mm to 105mm focal length. (A fold-out adapter can broaden this to 14mm or 17mm.)
For these comparisons, both flashguns were set to 50mm focal length, when off-camera.

The images were taken with a Nikon D800 and a Nikkor 50mm f1.8D AF lens, mounted on a tripod. The camera was set to aperture priority, auto focus and auto white balance.
Metering was set to matrix, as the aim of these initial tests was to investigate the control of the MK910, either as commander or as slave.
The test images are jpegs straight out of the camera, with no processing other than resizing for uploading to this gallery.

The tests comprised the following:
1. Shots with the flash mounted on the camera.
2. Using the MK910, mounted on the camera hotshoe, operating in Commander mode as Master, with the SB800 on the left operating as Remote (slave), under the control of the MK800/D800 combo.
3. Using the D800 in Commander mode, via the on-board pop-up flash, the SB800 as Remote, Group A Channel 1 on the left of the camera, and the MK910 as Remote, Group B Channel 1 on the right of the camera, as shown in the 5th image (Set-up) below.

Observations:

1. Flash mounted on D800 hot-shoe.
For comparison, the first shot is using the on-board pop-up flash in the D800, which exhibits a degree of underexposure.
Next 4 images are using the MK910 mounted on the D800 hot-shoe, followed by 4 images with the SB800. In each case, shots were taken with flash output varied using the flash controls, at 0EV, +1EV, -1 EV and -2EV.
With the MK910, there is much less variation in the resultant exposure levels, compared with the SB800, which suggests that calibration of exposure levels in the MK910 might not be as accurate as expected (assuming the SB800 is OK!).
Interestingly, the images taken with the MK910 appear to be more saturated than those with the SB800.

2. MK910 on camera in Commander mode, SB800 as Remote to the left of the camera. D800 set for TTL control of the MK910.
Note that in Commander mode, the MK910 allows TTL control of the Remote SB800, BUT it does not appear to provide TTL control for itself, as Commander.
The MK910 flash can either be switched off, or controlled manually, dialling in full flash (1/1), and varying fractions down to 1/128.
The second set of test images was taken with the MK910 in manual mode, at full power - 1/1 - and at 1/32, 1/64 and 1/128.
In all examples, it appeared to overexpose. The main conclusion I can draw from this is that the MK910 does not appear to provide a fully compatible Commander facility.
(Although it is entirely possible I am doing something incorrectly, here! And if anyone has any suggestions, please let me know.)

3. D800 in Commander mode, with SB800 and MK910 as Remotes, one each side of the camera, as shown in the 5th image below (Setup).
Tests were done first with the onboard flash, all flashes set to