While removing hardware (spur mounts, cymbal L-arm mount) from a '60s Ludwig bass drum recently to start a little spring cleaning, two metal "sleeves" (right term?) dislodged from the shell. I'm trying to determine exactly where they were originally mounted. I'm also wondering why there wouldn't be three of these -- one for each mount that was removed. Is it because each spur mount would have one but the cymbal L-arm mount wouldn't?
Any "words of wisdom" as to what this part is, where it goes and how it's installed would be greatly appreciated.
Thanks in advance for your time and your help!