Quick ID, what I look for in online listings with limited photos;
USA front sight blade rear vertical line 90° to barrel.
Import rear line angled slightly ahead toward muzzle.
USA hammer spur lower line profile, from spur tip to hammer body,
heavier "S" more pronounced belly.
Import lower line slightly leaner more suttle "S".
USA frame loading cut out junction, where loading gate meets lower cut out line,
cut out line is rounded and flowing.
Import frame cut out line angles at this junction, has a slight peak.