While display and surface can display molecule models and molecular surface models, respectively, partially or completely, objdisplay acts on other model types (objects) that can only be displayed or undisplayed as a whole.
If an atom-spec is supplied, then any objects with model numbers corresponding to the specified atoms will be displayed. Otherwise, the argument(s) to objdisplay should be one or more model numbers or ranges of model numbers separated by commas. Note that a model_number is an integer and may be preceded by the # symbol (either with or without is acceptable).
objdisplay 1- display the object associated with model 1
objdisplay #1,5-8- display the objects associated with models 1 and 5 through 8
~objdisplay :/isHelix- undisplay the objects associated with any models with amino acid residues in helices
See also: open, display, modeldisplay, the Model Panel