Where is the Main Shutoff my Cutler-Hammer Breaker Box?
What you have is called a split-buss panel.

Code allows up to six "main" breakers or disconnects. The top six double-pole spaces in your panel are all main disconnects. One (spaces 9/11) is the "lighting main" which shuts off the bottom half of the panel.

The lugs at the top of the panel are unfused lines coming from the meter.

As a side note, the single-pole breakers in the top half of your panel are technically a code violation since that caused you to have more than six disconnects to shut down all power.