The earliest report to our knowledge of paywalled open access, whereby publishers charge merely to access or read 'open access' articles, was by Peter Murray-Rust who observed in August 2013 that Elsevier were charging 31.50 USD per article to some readers to access "open access" articles.
The journal involved was the International Journal of Hydrogen Energy.
At least three articles were implicated in this instance by Peter.
You can read the full text of Peter's report here: https://blogs.ch.cam.ac.uk/pmr/2013/08/12/elsevier-charges-to-read-openaccess-articles/
If you know of any earlier reports, specifically about charging to read or access open access content (excluding the re-use of open access content) please let us know. This is important history to document.