Like B152a1, but 2.25-mm wide (top), not 3.25-mm wide (bottom), windowed security thread.
It appears the printer used some left-over paper stock from the commemorative note with narrow thread as all other varieties of this denomination have wider thread.
300-dpi scans requested for any other prefixes with the narrow thread (only CQ confirmed at present), or with wide thread and prefixes near CQ so that range can be determined.
Courtesy of Alex Zlotin.