Looks to be about 300 Watts! Be careful you could burn the place down!
On a serious note, its impossible to tell from photos. Looks to be a cheap green laser so I expect it to not be too strong. Probably in the range of 20-50mw. The only accurate way to tell is to test it on a calibrated laser power meter.
Though there are a few things you can do to maybe get a ballpark estimate with those cheapo greens.
Does it sting your skin if you hold it there for a few seconds? If so its probably 40mW+
Does it light a sharpied match? If it does then its probably 75mW+
If it doesn't do any of that then, its just a low powered greenie. Though general lower powered ebay pens are 20-30mW.