"recycled prints," which are, I think, the most interesting print variations. There an old printing plate is modified to create a new image but using much of the original image. So you might replace Washington’s head with that of Lincoln, keeping the body and furniture, and thus save a lot of time and money in making a “new” print.
In the blog on map variations, I talked about different states of maps and there are similarly different states of prints. That is where you have essentially the same print but where the matrix used to create the image (be it a woodblock, lithographic stone or metal plate) has been slightly modified to update or improve the image.
This is a not uncommon thing for fine art prints, where an artist may run off a few impressions of a print, then decide he wanted to modify the image, so changed the matrix and ran off a few more. This can, of course, be done a number of times. In such cases, the early states are sometimes more valuable, as they are often rarer than the final version, but if the improvements in the image are significant, the final version can be more valuable.
Anyone who has looked at enough Currier & Ives prints understands that the color can varies from example to example, but there is another variation you can find in the same print which many are not aware of, that is size. One of the main ways to know if a “Currier & Ives print” is an original is to see if it is the “right” size, as listed in one of the standard reference listings. The problem is that there is almost some variation in paper size. This usually comes about because of the nature of the paper used and the history of a particular print.
If you take two instances of a print printed from the exact same matrix, the initial size of the image will be same. However, the papers used could have slightly different properties in their make-up which might mean they will change over time differently. Thus one might shrink a bit more than the other. It won’t be a huge difference, but there will be a difference. And of course, there can be the way the paper was treated; if one is exposed to lots of moisture or heat or whatever and the other not, again, the paper will likely change slightly differently over time, creating a slightly different image size.
And, a further confusion in this is that firms like Currier & Ives sometimes used different matrixes for the same print! In order to be able to run a lot of impressions at one time, the firm might create a second (or third) stone using a transfer process so more than one press can work at one time. In the transfer process, there can be some variation introduced, either because the transfer is slightly flawed or because the new stone might have needed to be touched up or whatever. That is why sometimes you see two examples of exactly the same Currier & Ives print, but where it is the image itself that is slightly different.
And along this theme, you can have the same image used for two prints of different titles. Why waste the same image when the girl shown can be Emily or Mary Jane? This was done by transferring the image from one matrix to another and just changing the title.
There are many more reasons that examples of the “same” print can be variations and for commercial prints this tends not to be an issue that affects value. It is just a factor of prints being multiples. Even if the physical objects used to make the prints (matrix & press) are the same, the prints themselves live a varied life after they have been printed. That often introduces some differences that can be interesting, but rarely are of significance.