The model numbers were assigned in 1957, but model-marked guns did not begin shipping until sometime in 1958, so there would have been some K-22s that were not Model 17s that shipped in 1958. Clearly yours is one of them.
Having the original stocks, documents and tools does add value even though you don't have the original box. But the biggest factor will be the actual condition of the finish. This could easily be a $700 gun if it is up around 98% condition.
The target hammer and trigger don't add much, since they were very common on these guns at that time. The K-22 was, after all, a target revolver. However, they are nice features and do add to the attraction of the gun.