Having compared scans of the notes, as well as images of the notes under UV light, we'll take a look at the notes with backlighting.
All four notes display similar qualities. The parquet watermarks are clear with blocks of four lines running diagonally alternating 90 degrees every other block of four and the back ink is clearly visible through the face and appears violet. I don't particularly see anything off about any of the notes when backlit.
Second P # 83x
Third P # 83x
I've also viewed all the notes under IR but the results are the same as the backlighting test, all appeared to be the same with no IR features and no visible ink, blemishes or alteration. I don't have a good way to capture IR images yet so I won't be posting them, you'll just have to take my word on the results. If someone REALLY wants me to post IR images of the notes let me know and I'll see what I can do. I will also add that the notes all measure the same and the paper quality seems to be on par with other 5 Karbovantsiv notes from 1991.
In the end I see nothing conclusive and can't say whether or not these notes are genuine. Some of the smudging and staining could lead one to believe that these notes were altered but I tend to think not, I also find the possibility of these notes being missing print errors a stretch. To me the more likely possibility is that these were purposely printed on only one side but for what purpose. The back design seems to be an exact match to other notes, granted it is a simple design and could be easily counterfeited I just don't feel that is the case with these. I might give these another go with PMG but I will have to contact them and see if sending in all three examples, and a certified note if that helps, would be beneficial and perhaps if I submitted them as something besides P # 83x (missing face printing error). We'll see. My best guess at this point is that these are a printer's proof or scrap.
Now to see what's going on with the two different security fibers on the control note.