Yep, I can also confirm that there should be two different oilcans, moulded in black plastic, that fit into those holes. When these locos were new the two cans came in a baggie with the driver figure, and a tiny tube of plastic glue to fit them in place with.
Yours looks to have the driver, Roly, so I assume the two cans have gone missing sometime in the loco's life, probably a previous owner didn't glue them on.
Jon.