79 sr500 help with part identification

[Reds]

Hello, i just inherited my Grandad's old sr500 from his racing days, and would like to get it running again, been slowing cleaning the bike up, and while attempting to strip it down, one of the pieces broke, i am somewhat unfamiliar with bike, but to me I think it was the ignition coil? was attached to the spark plug, sorry if this seem really obvious. I am looking for a replacement and just making sure I am buying the correct part, any help would be appreciated.

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79 sr500 help with part identification