According to an article on JapanToday dated 8 May 2014, on 12 May the Bank of Japan introduced a new 5,000-yen note like the existing notes (B366a), but with high-tech anti-forgery features and enhanced convenience for visually impaired people. This note has a 1- or 2-letter prefix, brown serial numbers, and different shaped seal over hologram at lower right front.
Courtesy of Mark Irwin.