Unfortunately, there are a lot of little details that can seemingly only confuse.   "Always" and "Never" are always dangerous and should never be used.
The earliest blades are dated 1894 and were actually blued originally (like the 1873's).  Many or most were eventually refurbished and the blades stripped to bright.  I have a couple that show some degree of blue, but both are sharpened and probably should have been returned for refurbishing - or maybe they were too far gone to be worth the effort.
There are essentially 4 models of scabbards and all were blued. The earliest was a hook to simply fit over the belt.  There was no limiter rivet, so the rotation potential was 360 degrees and the opening for the blade was actually slightly tapered to match the blade.  The second model was still a hook, but the rivet was added to limit the rotation.  The hole became a simple rectangle.  The Third used two wires to serve as a spring attachment.  The wires were "pinched" to fit between two cartridge loops of a Mills style canvas belt.  The last type still used the two wires, but they were not "pinched" so that they would straddle an actual cartridge loop (containing a cartridge) in order to be the tightest hold of all. 
The rivets used for the wood handles show two variations.  The original style from 1894 to, I think, 1898 or 99, had the domes of the rivet ground flat.  After that time, the domes were left intact to simplify production.  If a blade dated with the earlier years shows the domes present, it's just an indication that the bayonet had gone back to the arsenal for repair or refurbishing.  It has always been a puzzle for me as to why a sharpened blade is such an anathema to collectors, when it is a sign that the bayonet had possibly been used in the field.  We've had photos on this forum showing troops with Krags nearby while they were sharpening their bayonets..