This is the control box for the interval bomb release. For bomb load that needs to be released slowly instead of all at once, the bombardier set the dails of this control box to causes the bombs to be releases in the specified interval.

Located on the interior left side of the bombardier compartment just below the window, this control box is approximately 8-inches wide and 4-inches tall. You can see a small portion of this control box through the window from the outside of the aircraft.

Click image to enlarge.