What is a EHS-7 fastener call oy?

[Barbqman]

Can anyone help me figure out what type of fastener is this call out (EHS-7)on a Boeing drawing?

 

[WKTaylor]

Per a ancient [1970s era] 'purloined copy' of an old Boeing document, EHS = BACR15AZ [flush head lock bolt?]

Regards, Wil Taylor

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