I'm not really a Premier expert but I am a bit familiar with the 70s Premiers. Premier Drums Community is the FB page. I just seen what I think is the mounts that you are referring to, and that particular Era they'd used that design for the cymbal arm also along with the bass drum legs and that was before the early 70s if I remember right. I've got a Powerhouse set from '74 that had the changes I mentioned earlier. The 3 hole design just wasn't strong enough and Keith Moon, Jon Bonham beat the crap out of them, they just couldn't hold up.