The finish quality on the trigger housings has improved recently with the most notable feature being a redesign of the safety catch at the extreme rear of the housing. I do not know when the redesign took place but we have seen a large proportion of the new design housings recently.
This is the old design showing a failed unit. There should be a little metal plate in the "pocket" at the rear of the housing - this has fallen out. The way the plate is normally secured is by a small plastic clip at the top front of the pocket. This has broken off in the photo and the metal plate has therefore popped free. This was a poor design and failed frequently.
This is the new design.
The metal plate is now larger and it is molded permanently into the plastic of the housing, a much better design. The improvement was made by modifying the original molds because you can still see the original plastic clip from the old design molded into the new unit at the top center of the plate.
This actually causes us a problem. Our metal sear clip is matched to the old design. It can be modified to fit the new design but this takes some skill and some special jigs. We will be having new sear clips produced to fit the new design but until they are available we will need to re-bend the original parts. SO, unless you really want to do the work yourself please send us your complete trigger housing so that we can do the work for you.