Alright. So! (composite) Gold leaf.
As this viola is supposed to be as close to the original as we can manage, I made stencils from the images of the painted/gilded ribs, which are posted online--then, using the measurements from our own instrument, stretched the images to fit, in photoshop. Then I made myself stencils from the printouts, and painted in, darkly, where the gold for the letters should go; made sure the paint was tacky enough that the leaf would adhere, and then laid it on in sheets late last night. Today when I went in, it was dry enough to dust off the excess--though not yet dry enough to get a good, antique-looking sanded effect.
Apologies in advance for the image quality--as it turns out, it's hard to take pictures with your weaker hand while wielding steel wool in the other!
Most of the gold leaf will actually get worn away, when all's said and done; in many spots, only a speckly-distressed surface will remain.