The model is one in a series by Canadian Ken Uhrig. You can still see most of the line here:
The Spitfire Emporium (Kitchener, Ontario, Canada).
I think you may be very lucky to have picked up one of the Harvards left. The source above doesn't seem to have it, although they have a photo of a finished, beautiful, model (attached).
I have the Fleet PT-26 Cornell, and your description of the model seems very much the same. Mine is dated "9/05" which would seem to indicate a much later date than I would have thought.
The kit is very much like a hand-drawn, hand-painted, one-off work by the artist himself, although the pencil-drawn (sic!) parts probably have been copied on an ordinary office copying machine.
Parts are printed (copied) on coloured paper (yellow in my case, and yours), and many details hare hand-coloured with what seems to be either water-colour or felt-tip pens. In addition, the national insignia come hand-painted (I believe) on thinner paper, just like you reported.
The technique is much like the models by Robert J. Kaelin (New York, US), although his models are drawn with ink before copying on coloured paper. In addition, his models always come (came?) with an assortment of straws and floral wires for sundry details, plus very detailed, illustrated, step-by-step instructions. His designs are quite unique in other aspects as well, since they do not use any laminating on thicker card. The models are mostly from the 1990's.
Both Kaelin and Uhrig have designed most of their models in the sensible 1/24 scale (although Uhrig reverts to 1/32 for larger models such as the Spitfire).
It seems almost a shame to put a knife to such works of art. Uhrig's models in particular retain a very "quaint" quality in comparison with the computer-aided, professionally printed range available now. Yet the finished result seems to be excellent to judge from the photo below - and your build, which I will follow with great interest.
Leif