In old instrument panels, needles and faces behind glass are usually quite clean except from some leakage at the edges if there is no rubber seal behind the glass.
The glass covers get very grimy, and are wiped up with an impatient work glove when the grime impairs readability, so the grime accumulates around raised edges, and the glass gets scratched over time.
Old bulbs in instrument panels get grimy too, resulting in yellowish light.