While there is some rubber inside a pneumatic golf ball, its not a solid "rubber core" ball because its center is a rubber bladder full of air!  But what also sets this ball apart beyond its core is its cover is one of the few made from para rubber, not gutta percha.

This “The Pneumatic” golf ball is all there, but most of the original lettering on the poles is tough to read.  Enough of the "Goodyear" remains on one pole to positively identify that name.  Fortunately the word "Pneumatic" still remains on both sides of the equator so the ball can be positively identified. The ball was originally painted red, for use when dew, frost, or daisies, could come into play. 

The Goodyear Pneumatic ball was covered under a patent filed on Sept 11, 1900 by Addison T. Saunders who assigned half of it to Frank Seiberling, the man who founded Goodyear Tire & Rubber in 1898.

This ball shows wear, but it's still a worthy ball. It has been used but does not bear a strike mark.  Pneumatics are one of the most creative balls produced and not many remain.

Ball is shown on the far left in the second row from the bottom in the accompanying group image.