Smith & Wesson introduced the Sigma gradation of recoil-operated, locked-breech semi-auto pistols in 1994 with the Sigma 40, followed by the Sigma 9. Sigma pistols bore so much similarity to Glocks that users could reportedly interchange many parts between Glock and Sigma models.
The similarities were so extreme that crowded pundits referred to the Sigma line as "Swocks", a playful contraction of S&W and Glock. As a result, Glock initiated a patent Smith & Wesson Sigma infringement lawsuit against Smith & Wesson, which paid an undisclosed sum (the amount of three million dollars has been theorized) to Glock for infringement of their patents. S&W thereupon received the rights to continue the production of Sigma line.