I stumbled upon the old National Treasure research thread and decided to give this prop a go.
A fairly easy and cheap prop to make -
$30 for the Townsend glases.
$12 for a two pair of the gold plated loupes.
$21 for 3 colored lenses from Anchor Optics.
$3 for a cheap acrylic frame which I shaped into the clear lenses of the glasses.
used my dremmel with a small steel brush bit and took the gold plating off of the loupes.
Took any remaining gold off with some steel wool and fine sandpaper.
Also used the find sandaper to remove the paint off of the glasses.
Used some Aluminum Black to weather the metal loupes and glasses
used a small micro hand drill set and drilled the holes for the loupes. (I was too worried about using and electric drill so just slwoly drilled it by hand)
shaped the glasses lens housing by lightly hitting it with the rubbery handles from a pair of plyers.
Big thanks to Droidboy for some lens info.
The best part is, I tested these specs out on a 3D Iphone app and it works just like 3D glasses.