Premier used several different mounting systems over the years. Does yours have a large hole in the center of the three mounting screws or are there just three mounting holes? That will help to zero in on the date of the mount and which one. 

Hi, it has a hole in the middle. Sorry, I should have mentioned that. 

I recommend checking with specialized drum parts retailers or forums dedicated to vintage drums. They often have resources or members who can provide specific dimensions for the mounts they sell.

I suggest consulting with vintage drum forums or speciality drum parts shops. They frequently have members or resources that can give precise measurements for the mounts they sell.

You might want to check out any vintage drum forums or local drum parts stores. The exact dimensions of the mounts for sale can often be obtained from their members or other sites.

Three legitimate posts by actual human beings and three posts by AI bot accounts. 

Yeah, I received two vacuous comments from the HAL9000 on my Dynasonic post.

This is only going to get worse.

Yeah, very frustrating. I tried reporting the bot accounts everyday for a while and some got deleted, but most are still active. I think I'm about done, unfortunately.  There are only a couple of us still posting, and this constant barrage of bot accounts has no doubt driven some away, and certainly doesn't make the stray human that signs up to want to stick around.

Hang Tough! The lazy asses using AI bots are going to be identified by tracking some day. But to answer your question about the mounting ID problem I would suggest going on the vintage drum catolog website. It's going to take a bit of time but go through them and find the sets that used the same mount. Premier if I remember right used it in late 50s possibly into the late 60s, when they changed to the trilock mount I believe. It has been a while since I've been on there, I could be using the wrong name for it. Peter Hopskin is probably more familiar with it than I am. He's is on the FB page for Premier drum users. I probably got that group page wrong to, I don't get on there much either.