how do you tell fake five-lug Fuchs from the real-deal?

On the back side of mine, they say MADE IN JAPAN.

They are heavier then shit.

Real Fuchs will have the 911 or 951 part number stamped on them along with the "fox head" logo and a offset stamping.

Real 4 bolt Fuchs have a 914 part number, and the Porsche triangle logo EMBOSSED (not stamped) on the inside of the spokes. All 5 bolt genuine Porsche wheels are the same way.

The Cap'n

Not necessarily. I have a set of 3 XENON Fuchs that aren't all that heavy. They also seem to be pretty well made. I wouldn't mind finding the fourth

I agree - no necessarily. I bought two fake 7x15s that weigh only slightly more than my real 6x15s, which are the lightest Fuchs ever made at a mere 12 lb, I believe. I have not weighed them, but I just subjected them to the scientific test of picking them up in each hand, and bobbing them up and down. I am guessing the the fakes weigh about 3 lb more.

BTW, the spokes look different - more square than rounded on the large end of the paddles, and the outside lip is more flat than a real Fuch, which has a slight radius to it. As the others have stated, there will be the part number and logo on the inside of a real wheel.

I'd guess that both the 5.5" and the 4.5" Fuchs would be lighter.