Here's an original mounting instruction sheet for the 9N Cyclone Air Pre-Cleaner from my collection. The envelope it came in has handwriting on it that states it was installed in 1943. Note that it mentions the three air cleaners that were used on the 9N/2N - identified with a 'U'; 'D'; or 'H'. Also, this will not work on the 8N air cleaner.

Tim Daley(MI)

*9N653I* & *8NI55I3*