First off I’m not going to speculate on what standard printers practice was 100+ years ago because that is all it will be at the end of the day, speculation.
I will say from experience as an owner of a company that specializes in premium giveaways and retail products. There will always be manufacturing variances, the reasons behind such variances are many but often carry a common reason as to why. Most of the time it’s the most obvious reason FWIW.
From my experience collecting T206’s for 25+ years I can say that these cards have all sorts of little nuances that go missed. Many of which simply boil down to saturation of ink applied or missed ink all together.
There are dozens of little goofy things in this set that advanced collectors have privately chased for years under wraps to keep folks from looking for them to drive them up. Seriously it’s the magicians guild god help you if you are told something and tell someone else about that missing dot card…no kidding.
Example the cards below can be found with all sorts of degrees of clouds, glove colors, redness in cheeks etc. i.e. Ritchey/Doves.
Most all of them are simply cosmetic subtle changes that only by handling many of one card would you be aware of or notice. Some to most all have no real value either. Then there are those true cards with real visible striking differences which command premiums due to rarity.
There are also tons of faded backs I have a few Tolstoi’s in which the ink has been so lightly applied they look grey or brown…they are of course black.
IMO “True” color differences in backs are really stand out and not too subtle and also carry some common attributes in terms of series or subjects. A common rule of thumb is if you have to ask it’s most likely a faded version of its normal counterpart.
This from a guy who likes differences in backs and actively collects such anomalies and or variations; I see no differences in the Uzit brand.
I have been fortunate to handle and see quite a few from other collectors collections as well as own examples and I just don’t see it. In fact I have a few Uzits on hand now from a board member and like Tim posted above with the SC 649 there can be subtle differences but no night and day print difference.
Cheers,
John