My 2 cents on this topic:
The original Steyr M9 came out in 1999. It looks like this:
It has the trapezoid sights. The characteristics separating it from later models are: a blueish colour, a rounder trigger guard, a proprietary "box"/clip-on system for attaching a light (which is obsolete, as no one makes a light for it anymore. The original lights from 15 years ago are collectors items), and they all have the push-button safety right in front of the trigger guard (I believe they all have it). Some of these guns were imported to Canada. The barrels had to be special run for Canada, as the original design has a 4" barrel. Some have threaded barrels, some just have extended barrels.
Steyr came out with the "S" pistol at about the same time. It is a 3.6" barrel, with the overall size being about on par with a GLOCK 26. I have never seen or heard of a Steyr S or S-A1 pistol, of any calibre, being in Canada.
In 2004, Steyr came out with a redesigned pistol, the M9-A1, M40-A1, S9-A1, S40-A1. The M9-A1 and M40-A1 were extremely common in Canada for a time, starting in about 2006 and we kept getting them up until about 2009 date codes. I never saw any M357-A1 pistols in Canada, but there were tons of the 9's and the 40's. These all had extended barrels. I have never heard of any M-A1's in Canada with threaded barrels. Unlike the earlier pistols, these ones are characterized by a light gray finish, and a GLOCK-type rail that will work with most lights and lasers. There are some M-A1 pistols have have the push-button safety, but I don't think most (if any) of the ones that came to Canada with the extended barrels had that. When they first started being imported they all had trapezoid sights. Later some had three dot night sights. This is the one I used to own:
These ones, regrettably, had a lot of problems, and I say that as a person who likes Steyr and their products. Some had the weird loaded-chamber indicator on the breachface, which I personally believe is part of what made ejection irregular. But they had various problems with extraction and ejection. There are ways to fix them, by upgrading various parts and springs - lots of information at SteyrClub on this stuff.
The pistols got the reputation as lemons, that even a big price-drop couldn't overcome. Sales were never that great in the U.S. (and Canada) compared to the striker-fired polymer competition, and then they started to tank altogether. Steyr pulled the pistols from the U.S. market in 2010. Here in Canada we continued to see NIB M-series pistols after that, but they were always something like 2008/2009 date codes, and a price tag in the $500 range (trying to blow out new-old-stock).
New 2010-forward S, M and "C" models (the C is S-size slide and barrel, on an M-size grip) with a redesigned trigger, extractor and ejector started coming into the U.S. at the end of 2010. We never got anything here though. I doubt you will find a Steyr M pistol in Canada with a date code later than 2009. What we got instead was the L-series pistol, a few years later, which does not require a special barrel run for Canada. The L-series have all the upgrades that the other 2010-forward pistols have. I believe these started to come into Canada at the end of 2013. The ones that I have seen here have all had the 3-dot sights, white in the back, red in the front. People don't seem to like the red dot in the front. Some paint it over, some get Mepro-light night sights, so get trapezoid sights (from the U.S., I suppose, or off of an M pistol).
The way you can tell if your pistol has the redesigned trigger, etc. is if it has a roll pin right below the rear sight. No roll pin, old system.
