John Wanamaker's “Radio” golf ball is unquestionably the hottest ball ever made—or that will ever be made. It has a radioactive center!
"The quantity of radio-active substance which goes into one Radio Golf Ball. ...is the secret of this Ball of Mystery—the ball that never loses life or shape. $I each, $12 doz. John Wanamaker, New York, Sole Wholesale Distributor, U.S.A." [Golf Illustrated [ny], June 1918:45).
The Radio ball was patented in the U.S. by Ellis Miller, of London, England, who assigned his patent to The Radium Golf Ball Company, Limited, New York, N.Y. According to Miller’s patent (No. 1,260,788) granted on March 26, 1918, his ball has a round core formed from “radio active material and an inert filling material” that retains the radio active material in position and prevents its displacement.
The May 1918 issue of Golf Illustrated (ny) states that the Radio golfball has a “Radium Center.” The article includes a “radiograph [x-ray] of the material used in the core of the Radio Golf Ball.” According to the June 4, 1918 issue of Golfing, the radium center used “radium salts”: "These salts have produced wonderful results in the intensive cultivation of crops, and their use in golf balls, though not giving any mechanical aid in the matter of distance, vitalises the rubber and keeps it in perfect condition."
And such is the case with this ball—in perfect condition, still in the wrapper!