Judging from the wiring diagram in the close up photo of the panel, it shows two OC at each of the bus positions that are not the MAIN. It is in my opinion a 10/20 panel, and as much as I hate tandem breakers it would be Code compliant.
Being mounted sideways does not comply.
I would recommend, not require, replacing it anyway, to get more wiring space, and to get away from the tandems that have such limited contact with the bus.
