The LP/Cs with large INERT markings on them are expended M26 or M28 pods used for handling training or displays and demonstrations. Sometimes tube caps are recovered and reattached. Certainly any with open tubes and inert markings are fired pods kept for training. The M27 trainer pods have ballast in some tubes and caps on all of them.
Look at the other markings in the kit. They should have either M26, M27, or M28 markings. If M26, the only time they would be marked with the big inert label is after they have been fired. They would have the upper left corner of the frame painted yellow. This would indicate an HE loading, but because it isn't there they use the large inert markings.
The M27 trainer will have M27 markings with a bronze paint swatch on the corner and markings with 1-inch high INERT TRAINING ROCKET POD markings, so no large inert label.
The M28 practice pod has M28 markings, and given that it has a live rocket motor with a live smoke warhead, it would NOT be an inert munition. It would have a blue paint patch on the corner, and could have the large INERT label after firing. That looks like what is in this photo:

KL