Four (4) issues of The National Geographic Magazine.

February, 1916.
March, 1917.
April, 1917.
May, 1917.

"To carry out the purpose for which it was founded 27 years ago, namely, 'the increase and diffusion of geographic knowledge.'" - Gilbert H. Grosvenor, Editor.

The illustrations in the 1916 issue are photogravure.  Defined as printing a photograph using a copper plate.  The 1917 issues proclaim some photos are printed in four colors.

Please examine the contents cover and the inside pages using the eBay photos.

Thank you!