It is possible that your grandfather carried a prsonally owned .32 caliber pocket pistol through the war, but I doubt it.
I do know the .32 Clement seems to be a rarer gun than the 5mm or .25 caliber models. Its chief "claim to fame" is that it was the gun on which S&W based their .35 Model 1913 pistol. Because most of the good ideas in pocket pistols had been patented by Browning and Searle, S&W went looking for a different design and found it in the Clement to which they bought the patent rights. Some Clement features are seen to this day in the S&W .22 caliber auto pistols.