SEM brushed DC servo has stuck brake & disassembly help
You need to mark the end bell and frame before removing the end bell to make sure it is aligned the same way when reassembling.

If this is a permanent-magnet motor, the rotor will be drawn to collide with the stator magnets as soon as it can move once the end bell is no longer holding the bearing in place. You need to work out a way to keep that from being a hard collision.

If you are going to remove the rotor, the brushes need to be moved away from the commutator. You may need to insert some kind of spacer material in the air gap so the rotor won't be held against the stator magnets.