Regarding duplicating an original decal, I would like to offer this
suggestion.  First off, if the original decal is still intact, why
not try to save it or have a fine artist touch it up with matching
pigments?  If the original is too far gone to salvage, the following
method can work.

Take a photograph of the remaining decal, and scan it into Photoshop.
Solidify all the areas of a particular color (there are probably only
two or three: black, gold, and maybe silver).  You will need a piece
of original art for each color, _exactly_ the same size as the original
work.

You take this output to a large graphic design house and tell them
you want a transfer INT made for each color.  These are basically big
rub-off transfers, available in any PMS color you can mix, as well as
metallic colors.

Rub off these transfers onto the instrument registering the colors
carefully, with the base color first, then the next color, and so on.
When you are finished you will have an near exact copy of the original
transfer.  You have to be very careful, as INT's are delicate.

After this, you can spray finish over it.  It would be wise to have
a few test INT's made first to get the hang of laying them, and to make
sure your finish doesn't dissolve the INT.  Obviously you would need
to hire a graphic artist to do the mechanical work if you are not so
inclined, but the result is well worth it.

John D. Rutoskey