I had it once before in my 10 years working as a patent attorney, and for the second time yesterday: The patent examiner cites a patent application as prior art that actually isn’t prior art.
In yesterday’s case, the application had already been rejected by the examination division. We managed to reverse the rejection on appeal, and the board of appeal had remitted the case back to first instance, stating that the claims were patentable in view of the prior art cited so far.
Back in first instance, the examiner did a top-up search and cited a US patent application as new prior art. In his view, the claims lacked novelty, or at least inventive step in view of this document.
But the alleged prior art (the US patent application) was only published three weeks after the filing date of the application (an EP application).
This will be a rather short reply brief…
Takeaway: Always double check if the prior art you are confronted with was actually pre-published.