Percussion
Bonham often mounted a cowbell on the bass drum hoop and fixed a 'ching ring' (headless tambourine - see image above) on top of the hi-hat.
Before regularly using timpanis for live shows, Bonham would play on timables or Natal congas live.
Many more details can be found in Welch & Nicholls' amazing book - 'John Bonham A Thunder Of Drums' Which you really ought to own!
If you have any other info on the equipment Bonham used, or have noticed mistakes - please contact me