Same Problem exists in the Classic Car world. If classic cars had to be restored with all original parts there would not be any classic cars left. A car that is "All Original" is worth more but its the buyers job to verify that. Same thing for historic guns. We are all not lucky enough or rich enough or old enough to have acquired 100% original Krags. I recently restored my Grandfathers Krag and was delighted to be able to acquire period correct parts to put it back as close to original as i could. I have no intention of selling it. But who knows when i am gone what will happen to it.  In the case of this carbine sight that poses a bigger issue as the originals are very expensive. I would guess that these will make it onto ebay and gunbroker as originals. This is a crime. For someone restoring a sporterized gun the SS sight would be a great find. So ethically i do not think we can fault SS but we must be aware that the reproductions exist. Not sure what someone is to do. In some cases it may be nearly impossible for normal people to discern the difference.