I once owned a Cremona A-roll coin piano which had an original bottom
cover board consisting of a heavy frame containing five recessed panels
about three-eighths of an inch thick.  Both the frame and the panels
were cross-banded and veneered, with the core wood being either poplar
or oak.

The two left and right panels I replaced with quarter-inch thick plate
glass, and above the centrally located motor I installed a vintage
light fixture with a low-wattage bulb wired to light up whenever the
instrument was playing.  Up above were two more low-wattage bulbs
between the three leaded insets (containing both stained and beveled
clear glass), wired to be on whenever the establishment was open.
The effect was quite appealing.

Many lower cover boards, as well as doors on cabinet style
(keyboardless) "nickelodeons", have been replaced over the years with
simple frames containing glass, because the mechanisms inside are so
fascinating to watch.  If an original cover board is missing, that
would be one logical way to go.  Otherwise, because there were so many
variations in what was done by each manufacturer, it would be worthwhile
to seek out other machines of the same make, model and approximate age,
with the hope of finding something suitable to copy.

Jeffrey Wood