Re: Missing STC and 337 found during annual
Just an many people incorrectly thought that, under the now-dead FAA-CAA bilateral treaty, you could just install an STC'd part to a G-reg without getting an AAN from the CAA (and many did), many people think that one can do the same with STC'd parts on an N-reg. The fitting of such a part to an N-reg is done under a 337 or something higher.
Normally it isn't a problem but as I mentioned, this is an area where somebody pedantic can ground your plane for weeks or months or years. You need to locate an A&P/IA who understands the process.