Ilford's data on Delta 3200 shows an ISO if 1000.

For Kodak this was copied from tech pub f32

KODAK T-MAX P3200 Professional Film is specially designed to be used as a multi-speed film. The speed you use depends on your application; make tests to determine the appropriate speed.
The nominal speed is EI 1000 when the film is processed in KODAK T-MAX Developer or KODAK T-MAX RS Developer and Replenisher, or EI 800 when it is processed in other Kodak black-and-white developers. It was determined in a manner published in ISO standards. For ease in calculating exposure and for consistency with the commonly used scale of film-speed numbers, the nominal speed has been rounded to EI 800.