The baseplate is held in with two screws. On removal, a large number of parts become free to fall out. Note the front bogey, and its washers; the contact strip; 3 main drive axles with tyres on the front pair of wheels; 2 smaller gears seated between the drive wheel axles. This 2-6-2 model has bogie wheels at the rear as well as the front - also with brass washers.
Note that as soon as you remove the wheels, the very delicate arms of the contact strip become unprotected. They are easy to catch, bend and damage.