This trigger was used on all Russian, Soviet, and Chinese models as well as most Eastern European models.

This unique sear was found on a 1923 Izhevsk updated Dragoon.  The origins of it aren't known but there is no evidence the rifle was ever in another country.  Few other examples have been documented.  There is a small coil spring between the base and the sear itself.   The stock required some extra relief in front of the trigger for this sear to fit.

courtesy of Greg Kirkman

This is a Finnish made trigger and sear that are pinned together.
The trigger is held in place by the sear.

This modified trigger with an extra leaf spring was found on a 1906 Tula M91.  While there are no definitive Finnish features or marks on the rifle, this trigger has similarities to known Finnish modified triggers.  No other examples have been documented to date.  Besides the extra spring there is a pin added through the trigger just forward of the usual trigger pin hole for the spring to bear on.  This pin is in the same location as the extra hole found in M28 triggers and this system may have been a forerunner to the mousetrap springs used on M28 triggers as they both server the same purpose.

courtesy of "blacst"

This trigger has a small hole that serves no apparent purpose but may have been for a pin and leaf spring as pictured above.  A mousetrap spring is added around the trigger pin which serves the same purpose.

This trigger has two small pins added for the sear to ride on.

The M24 uses a standard trigger with a mousetrap spring similar to the M28.

Apparently this trigger was modified for the M28 and then latter modified for the M39.

This type of trigger and sear is only found on the Romanian M91/30.  The Romanian M44 has a standard type trigger.