Drumshell picks have a tendency to cup or warp in sunlight. It's best to keep these away from any kind of light to prolong their longevity. All of the examples shown below, unfortunately, have 'cupping'...
3 different vintage silver-sparkle drumshell guitar picks.
Vintage blue-sparkle trapezoid shaped guitar pick
Vintage 'baseball pattern' drumshell picks
Vintage 'baseball pattern' drumshell 346 pick.
Vintage red-colored 346 drumshell guitar pick.
Vintage gray patterned drumshell guitar pick.
Vintage 'baseball pattern' small teardrop drumshell pick.
2 rounded black-striped drumshell guitar picks.
3 vintage pointy-tipped drumshell guitar picks.
2 more vintage black-striped drumshell guitar picks(pick on right shows bad 'cupping')
On right-another example of the 'baseball pattern drumshell pick)