Your comic would definately not be the only one. I couldn't guess at how many there would be. But I doubt any production defect would be "one of a kind".
However, some may be rarer than others.
For the comics that were printed on a "Letter Press", there was a single plate for each individual page, and each individual color.
Meaning there were 4 plates for the front cover. A black, a magenta, a cyan, and a yellow.
The same for each page of the book.
So a book with 32 pages and a 4 page cover would have a total of 144 individual plates. 36 black plates, 36 magenta plates, 36 cyan plates, and 36 yellow plates.
One plate per color, per page.