The term “original grant lands” means all of the public lands which heretofore have been or hereafter may be granted to the state by the United States for the support and maintenance of the common schools or for the support and maintenance of the university, the school of mines, the North Dakota youth correctional center, North Dakota state university, the school for the deaf, any normal school, or any other educational, penal, or charitable institution, and any lands which have been obtained by the state through a trade of any such lands for other lands. Original grant lands which have been sold on contract retain their character as such grant lands until the contract has been paid up and a patent issued therefor.