In the pictures shown, the frame area forward of the trigger seems to be 'cleaned up' but not finished like the rest of the frame. If the Fitz style trigger guard were a factory alteration, I would expect the finish to be better.
I have a Colt Detective Special from 1949 or so with a cut trigger guard and bobbed hammer. However, the forward trigger guard root is not really finished in the factory sense; much like yours. So I'm forced to conclude it's a "Fitz influenced" revolver rather than a Fitz revolver. It follows the Colt double action revolver tradition of being so badly out of time it won't reliably function.