Nikon S3 was introduced in March, 1958, which was one year after Nikon SP's appearance.
Since Nikon S3 was the base model of Nikon's rangefinder camera, SP, S3M and S4 and also was said to be a popular version of Nikon SP, they (S3 & SP) were planned to be presented within a short interval from the beginning (the product code of these two are Nikon S3 ; 26F1B, Nikon SP ; 26F2B).
Major differences between Nikon S3 and Nikon SP are as follows:

Range of frame mask - Nikon S3 : 35 to 105mm / Nikon SP : 28 to 135mm
Parallax correction mechanism - Nikon S3 : no / Nikon SP : yes

On the contrary, the viewfinder of S3 is brighter than that of SP, for the structure of S3's finder is simpler than that of SP's.
In addition to this, the shutter releasing sound was improved to be quiet that it was called "whispering shutter".

Well then, let's take a look at it.

• First introduced in March, 1958.
• Camera type : 35mm-format focal-plane shutter rangefinder camera
• Picture size : 24 x 36mm
• Shutter : horizontal-run focal-plane shutter with gummed silk curtain (ex. titanium curtain for the last lot)
• Shutter speed dial : single-pivot non-rotating shutter dial
• Shutter speeds : T, B, 1 - 1/1000sec.
• Flash sync contact : FP, X
• Viewfinder : Albada finder
• Finder frame : 1.0x / bright frame line - 35, 50, 105mm
• Film wind lever : ratcheted winding
• Rewinding : by the rewind crank
• Framecounter : automatic resetting type
• Body dimensions : 136 x 79.5 x 43.5mm
• Body weight (with f1.4/50mm lens) : 580 grams