The 5/16-18 thread is a common standard of modern hardware stores. It looks deceptively like 8mm (see below), which can lead to damage by trying to thread a more common part into a 5/16-18 receptacle or vice versa.
Besides appearing on a fair number of traps accessories, this thread was used on a lot of vintage bass pedal hoop clamps, notably Camco and Gretsch’s “Floating Action” pedals. Drum Workshop continued using it decades later when they made the DW5000 based off the same design, and have continued even as they designed their own branded wing bolts.
Ludwig has commonly used this thread on their 1216 and 1610 brackets and eye bolts. Their Consolette rail mounts (as well as other rail mounts) utilized 5/16-18 thread on the hex nuts and carriage bolts.
Surprisingly, many Japanese drum makers in the 60s and 70s used this thread on shell-mounted hardware such as leg brackets and tom post holders. Often these bolts had square drum key heads.
Latin Percussion continues to use this thread on a lot of their clamps and small utility hardware.