Where do you look on your circuit breaker panel to find what it rated at?

Ratings don't tell the whole story. Neither does the existence of a main breaker.

FOR MOST, with one main panel, the main breaker which will be a double will have a number like 100 or 200 written on each of the ganged breakers.

If it's the only fuse panel and is connected directly to the meter socket, the main breaker rating would likely determine the design load of the service.

The box should have a model number or info on he door that determines the capacity of the box. The number of poles allowed and the maximum main breaker size should be noted.
The service rating is also determined by the rating of the smallest link, You could have a 200 amp box, 100 A main breaker and wiring that supports only 100 Amps.

If this were a sub-panel, like what might be found in an apartment, you could have a 200 A breaker in the subpanel, fed by a 60 amp breaker and wired for 60 Amps. Therefore the rating would be 60 A and the 200 A breaker would just be used as a disconnect.

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