| http://www.w3.org/ns/prov#value | - In a preferred embodiment, a crayon or marking pencil 1 such as is depicted in FIG. 1 comprised of a solid radio-opaque substance 3 such as finely powered bismuth trioxide (Bi2 O3), uniformly dispersed within a waxy medium 5 such as paraffin wax, is used as a marker to apply a mark to the object to be inspected or marked.
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