I would try using a median or dust & scratches filter to reduce the noise on the coin.
The other issue you're going to face is that you're not actually using a bump map, you're just using a picture of the coin. The shiny areas on the coin (like those around the eye) are going to appear 'higher' than the less shiny areas (like those around the temple) even though the less shiny areas may in fact be 'higher' than the shiny areas.
You might be better off trying to roughly hand paint the bump map, then place the image of the coin over your hand painted bump map and set it to one of the overlay modes (overlay, soft light, hard light, linear light) to add some of the original detail back in. You can change the Fill % to reduce the amount that is added.
Darby Edelen Lead Designer Left Coast Digital Santa Cruz, CA
First increase the resolution of your image and set it to grayscale. Yoo will then have to use the pen tool to draw masks for the shapes of the coins. Make a selection of the mask (eg: the background) , creae a new layer, then sample a color and paint with your flwo set to 0%, then selct the colro at the other end and paint in the other half.
Also take your original image ad do a find edges, then pu that on the top layer and mask that layer filled with black so nothing is showing. Yu can then paint back in the hard lines you needs with a thin brush. hard edge, slow 1 to 10% lots of pounding on your wacom.
This should take atleast 3 hours, and so I would recomend asking for the coin so you can scan it, or you may get lucky and do a google search on the images tab and find a better quality image. Tey to find ut who produces the coin to help your google search, as lots of images come up for "pope coin".