After completion of the CS-63 project, the Polish military received information from the U.S.S.R. on the characteristics of the T-62 tank. Their Soviet colleagues also presented a real prototype of the 115 mm U-5TS gun and documentation for its production. As a result, the Poles decided to create a new tank based on the CS-63, equipped with a powerful smoothbore gun. In 1967, the project documentation was being finalized for building a prototype; however, development was halted due to the decision to build a more powerful main battle tank.