Think mechanical.
Create a machine (maybe with hard rubber surfaces) that bends a bar or coin just a little. Gold would bend a few thousandths, and the coin or bar would rock on a flat surface after the abuse.
A W fake would shatter, or just deform the skin visibly, or not bend at all, lying flat on the surface.
Tungsten might have lots in common with gold, but the detection methods are third world, and bulletproof. (like poking a needle into a bar).
Just flip it in the air or drop it on a table. Tungsten (or anything else) will ring funny, or not at all. I agree with the poster that said tungsten is a bigger risk on large bars and ingots. Not so much on coins.
I also think that this is a hit piece for precious metals. PM's are a store of value and while they are not as portable or liquid as greenbacks have been, the people who are buying PM's think that the situation might change.
I tend to agree. I also hear those who espouse brass and lead. Same portability problems, but maybe more barter possibilities. Keep an open mind...