I browsed a recent item advertised on eBay, and the advert was selling an Iraqi FDC, shown in the picture, and claiming that this is a cancellation error and selling what should be a relatively cheap item for many times the price it should cost.
The item has two cancellations on the stamps side, one of them is the wrong cancellation for that issue and one of them is correct. There is another correct cancellation on the opened part of the envelope.
Is this an error? I do not think so, it is very wrong to call it that.
Those post mark markers are very common in Iraq and you often get the same FDC but with a different post mark (cancellation). Anyone who gets hold of one of these could do what they wish with the post marker and use it on any envelope, cancelling any set of stamps they want.
This is not a genuine error, but rather someone deliberately cancelled the stamps wrongly, either for the sake of it or for the sake of passing it as an error.
In reality errors are in the stamps themselves, not on a hand made FDC in Iraq where there would not be much control on what is done and who does it.
It is really disappointing that this is being sold as an error.