Referring to the non-ctl twin breaker installed in this service equipment, is this a violation even though the six disconnect rule has not been violated? Secondly, would it be in violation to install a breaker upside down on top even though the equipment is designed as such?
(yes I see the doubled neutral/ground terminations)

I would be more concerned about the interrupting rating on the duplex breaker. I can't read the label. It might not be suitable as service equipment. There are extra holes, moving the neutrals is easy. To be able to use those empty slots, the panel needs to be mounted sideways.
Not a lot of wiggle room in 240.81

Thanks Greg, I knew 240.81 didn't include any exceptions, I wonder how long they kept making that style after the code change which I understand was in the 70s. I hadn't thought about the interrupting rating.

I looked and that is probably a Q2020 with a 10KA rating. That should handle most situations. (same as the 200)
As I said, you can install that so the breakers are horizontal and it would be OK. I wonder if the instructions say that?

Being that it's a 3R meter main I don't think that is an option.

That does beg the question "how old is this"? I have an old GE panel like that but I suspect it was installed when they built my garage in 1970. Is there any guidance on the label about what breakers it supports in those top positions?

Are you asking about the open stabs above the single pole 20A, & the 2020 Twin? If yes they cannot be used under the NEC, since ON is required to be up on a vertically mounted breaker.

I haven't been able to get any more info, I am helping someone remotely. Not really doing work anymore except for family.

A Sieman smain with mounting for Square D ? Don’t think I’ve ever seen that

Just a feeling, but that panel “feels” like it’s from the seventies.

Reno:

Where do you get Sq D from??

Ahh, you caught me!

I usually use Square D service panels from my local Square D carrying electrical house. Gray bar is an example. BUT ..

On my recent service change the local utility required a panel with a knife disconnect inside the utility portion. I was supplied with a Milbank panel with a Square D main. (According to Milbank that panel was required only by Amerindian (Missouri and southern Illinois).

Reno:

Wasn't trying to catch ya, just looking at the pic I could not see any Sq D. (Was and still is my fav)

You’re right, HotLine. I got sloppy and di- dn’t look closer at the pic. (I get any more senile I’ll have to try politics!)