Your Defender 38 with that serial number (6079), the "gold bead" front sight and that type of marking was made in the mid 1940's, your's is probably late 1943 or early 1944. At that time it was called the Model 25 and was based upon the SPORTSMAN .22rf model. It is chambered for the .38 S&W - 146gr lead round nose and will also take the .38 S&W-200gr British military round of that time (.380-200). This series was one of the few revolvers/handguns that H&R continued to make through out WW2 and was intended for use by civilian Security personnel - plant guards, bank guards, civil defense personnel, etc. It was discontinued around 1946 - but the design was resurrected with a manual ejector in the early 1960s as the Model 925.
The spring that is missing is a coil type that fits around the "guide rod" which is still installed in your gun. These springs are somewhat generic - but must fit between the push head at the top and the cut out in the frame with a little slack - check the attached pic. The same spring can be found on SPORTSMAN revolvers from the same era.
The grip that is missing was originally made of black nylon and was molded in one piece. These are somewhat difficult to come by - they do show up occasionally on the on-line gun auction sites as well as e-bay. Check the attached picture. A one piece wooden grip from that era will also fit.