Made by William Currie & Company, Eclipse Patent balls were produced under the third patent ever issued for a golf ball,  William Currie’s Dec 20, 1877 British Patent 4,838.  This patent covered including additives mixed into the gutta percha, such as ground cork,  ground leather, vegetable fibers, etc.   The fact that the Eclipse is not made from pure gutta percha makes it a composite ball, although the actual ingredients and amounts included in the various Eclipse balls are not known.

The auctioneer dates this particular ball offered here to the late 1880s.  Currie made the Eclipse ball for a number of years, into the early 1890s.  This one is magnificent, with no strike marks and strong lettering as shown.