This sounds contradictory. Let me explain.
Over the years, collectors have put an emphasis on gum. The Scott catalog now lists prices for both never hinged and hinged stamps for many early US stamps. In my opinion, this is a bit of a misnomer. It should be “pristine gum” and “not pristine gum” because original gum that has not been disturbed at all is never hinged. Meanwhile, a hinge mark, disturbed gum (due to exposure to humidity or other factors), gum with heavy ink offsets because another stamp adhered to the back of it, and so on and so forth are not “never hinged” stamps. To me, a never hinged stamp means gum that is 100% undisturbed, natural or otherwise.
Sometimes though, a hinge mark does not detract from the value of an item. Let me explain.
Some early US stamps still have selvedge attached to them. Some collectors like this extra selvedge, especially if it has any plate markings on it such as a plate number. Suppose the stamp itself is never hinged. However, someone hinged the selvedge. To me, this stamp still qualifies as a never hinged copy. Why? The hinge is in an area that is not affecting the stamp itself. Remove the selvedge and you definitely have a never hinged stamp.
Suppose I would price this stamp for $100 without the selvedge. With the selvedge and the plate number, I may add a premium and price this stamp at $125. Because the hinge is on the selvedge, I reduce the price to $110. My point is that I’m adjusting the price a little because the hinge is in the selvedge, which is a component of this stamp, albeit small. But the stamp itself is never hinged and should be priced this way.
When a plate block has a hinge mark in the ungummed area of the margin (ungummed areas are common on flat plate printed stamps where the gum does not extend all the way to the edges of the margin), I also consider that plate block to be never hinged. If the hinge is in the ungummed area and hasn’t negatively affected the plate block, someone could carefully remove the hinge and with some very delicate care, remove any traces of gum residue from the hinge. With proper care, a hinged plate block could be turned into a never hinged plate block.
Suppose a never hinged plate block catalogs $1000 and a hinged copy catalogs $500. In this case, I may price the plate block at $800. Yes, the hinge is there. In my opinion though, it’s not affecting the gum and hasn’t altered the appearance of the block. In my opinion, there is some premium to this unobtrusive condition.
In conclusion, a hinge mark is an insignificant part of the stamp that can be easily worked around. Sometimes a hinged stamps needs to be factored as a never hinged copy.