Actually, there was. See S&W add below...



The first S&W 640 (J frame) no dash models used by the Treasury Dept. as back up guns were purchased by the agents, at a special rate, under an agreement reached between Treasury and S&W. Treasury furnished the ammo for qualification and carry, which was the round in question by the OP. Later, Treasury purchased the 640-1, and the same ammo was used.