Two golf balls in my collection, the Spalding Dot golf ball #241 and the Spalding Dot Diamond 90 golf ball #349, appear on the 1975-1982 USGA lists.
#241, Spalding DOT, (1975, 1979-1982 USGA lists)
Golf ball #241 has 336 dimples arranged in the traditional ATTI dimple pattern and has a soft balata cover, as evidenced by the appearance of numerous cracks on the surface. This ball appears to be the same ball as the one Hatcher(1) reports as the ‘1957 Spalding DOT’ with the scripted Spalding logo and the word DOT on the seam. This ball appears on the 1975 USGA list, is replaced by ball #349 from 1975-1978, and then appears again on the 1979-1982 USGA lists.
#349, DOT Diamond, Spalding 90 (1976-1978 USGA lists)
Golf ball #349 has the new durable Surlyn cover(2) as evidenced by the lack of cracks on the surface and has 332 dimples arranged in the icosahedron(3) pattern. Why does golf ball #349 only appear on the 1976-1978 USGA lists and then is replaced by golf ball #241?
I believe that Spalding replaced golf ball #349 with golf ball #241 in 1979 because the new icosahedron dimple pattern that appears on ball #241 was similar to the one that Acushnet Co. disclosed in their 1972 patent application(3). This application disclosed a golf ball with 332 dimples arranged in the form of an icosahedron with dimple diameters between 0.125 to 0.245 inches. The Spalding DOT Diamond golf ball #349 had 332 dimples with a diameter of 0.14 inches(4) well within the range of the Acushnet Co. application. Presumably Spalding replaced the #349 ball with ball #241 to avoid any infringement issues.
There are other Spalding golf balls in my collection that had 332 dimples arranged in this same icosahedron dimple pattern with 0.14 inch dimple diameter. They are the Spalding XL Top-Flite, #29, and the Molitor Spalding #537.
#29, Spalding XL Top-Flite (first appears on the 1979 USGA list)
#537, MOLITOR Spalding (first appears on the 1975 USGA list)
The Acushnet Co. patent application claimed a golf ball having dimples arranged in such a way that at least 80% of the dimples are less than 0.065 inches apart, and at least 55% of the dimples are greater than 0.0001 inches apart. I tried using my Pocket Comparator(4) to determine whether these Spalding golf balls were outside the range of the Acushnet Co. application but failed because it was very difficult to measure such a small distance for such a large number of dimples. However, it seems clear to me that the Spalding balls #537 and #29 need to be modified in some way to avoid potential infringement.
My next post will discuss what I believe happened next.
References
(1) M. Hatcher, The History of Spalding Golf Balls (Science Resort (SR) LLC, 2010, 2013, 2014), p 27.
(2) Robert P. Mollitor, US 3,819,768, June 25, 1974, priority date Feb 11, 1972.
(3) GB 1,381,897, Golf Ball Dimple Spatial Relationship, Oct 12 1972 priority date Mar 20, 1972, published Jan 29, 1975.
(4) See photo of my Pocket Comparator in my post published Nov 11, 2021, Golf Ball Collection-2.