Much more posts on trigger packs over at the FN forum, but got tired of some of the crazies over there. So posting my info here as well.
As far as owners can tell, FN PS90s come with three different trigger packs. No forth gen trigger pack with missing "auto sear" has been confirmed as coming from FN that way.
Generation 1 and 2 trigger packs function the same and the difference is the coloration in the plastics. Generation 3 trigger packs have a different cut in the hammer and also do not have the shelf cut on the "hammer sear".
Here are some photos of a stock Gen 2 trigger pack:
Ignore the arrow pointing to the
removable pin.
And for sure forget you ever saw the second arrow pointing to where the spring rests on the "hammer sear".
Here are some photos of a stock Gen 3 trigger pack:
Here are some photos of a Gen 3 trigger pack with easily available and cheap standard Steyr Aug hammer:
To make the hammers work in the trigger pack you just need to remove excess plastic from the hole the guide pin goes through as well as slightly widen the hole. Not bad for a $35 part :)
Here are some photos of a Gen 3 trigger pack fully modified to function just like a Gen 1/2 trigger pack. It has the Aluminum hammer as well as the shelf trimmed out of the "hammer sear".
While we may see droughts of several months with nothing available, Midwest Gun Works will usually have trigger packs in stock eventually. No need to spend big money on a Gen 3 on GunBroker if you can hold out :)