Overstamps are not uncommon, but it's surprising for a Model 53 to be an overstamp of a Model 17 frame. Are you sure it wasn't a 19? The front of the frame and crane are different between the 17 and the 19/53 because of the ejector rod housing on the 19/53.
Below are the Model 53, Model 17 and Model 19. Observe that the flat at the front of the frame on the 53 and 19 extends lower than on the 17. There is more material machined away from the frame on the 17 than on the 19/53.
Also although the Model 17 and 53 both have frame-mounted firing pins, the installation is different. (The Model 19 has a hammer-mounted firing pin.) The Model 17's firing pin is retained by a cross-pin through the frame, while the Model 53's dual-firing pin arrangement seems to be part of a separate plate that is inserted into the top of the frame, under the rear sight. Note the difference in machining at the top of the hammer slot.