There are how ever tale tale signs of these saws being fake and they are small
I don't know of any solid ones, I have seen a lot of the points people say on fakes and real ones.
-Stihl markings on muffler, although no white spot, wouldn't take a lot to fake.
-both black and grey coil wires.
-what appears to be the correct screws.
-"Stihl knots" on the recoil cord.
-I haven't actually seen a fake with "Made in Germany" on the recoil tag, but again that wouldn't take a lot.
3/8th pitch might be relevant. 070 was offered in 1/2" and .404", MS720 in .404". But who knows what is offered in Asia, Africa etc
The oil line may also be worth looking at, I believe if the saw has a plastic model tag it should have the press fitted oil line (and corresponding different crankcase), like the MS720. None of the fake saw pictures I can find give you a good look.
The serial number would probably be anyones best bet. Although it won't be registered I can give you an approx date for the serial and I would highly doubt it would be coherent with the tech updates etc
OR
Better yet don't buy what looks to be a new 070, you are asking for trouble, along with the Husky 365 Special and Stihl MS250, 380 and 381 it is known to have loads of fakes floating around.