SANDMAN PANELVAN (1977) HZ 4 SP (5 LITRE) - eBay - VIC

[Innuendo]

Mine is a 77 hz i thought the round button was from 78 up

I had a '77 HZ and it had a "proper" GTS horn button. But I didn't know it's full history and she had a few '80's mods so I'm not sure.
I'm sure others around here will set it straight or offer an opinion.