Another idea. The slide came from a Colt 38 Super that had been converted to a .38 Spl wadcutter target gun (these were used in a three pistol match or 2800 match). When that work was done, the gunsmith had to open up the face of the breech to accommodate the larger rim area of the .38 special cartridge which will allow the .40 S&W to fit (the case head of the .40 is just a little bit smaller in diameter than the .38 Spl.). I bought a Fusion barrel chambered in .40 S&W and had to do a little fitting but not much. It was almost a drop in fit.
The Colt 38 Super frame was eventually mated up to a Series 70 38 Super slide and remains that way. That left me with the other slide which as luck would have it, fit perfectly on an Argentine Sistema frame that you see above.