thank you for posting the pictures. have never seen the internal of a western arms/ lefever nitro single non-selective trigger. a couple days ago i stumbled across an old post here giving a written explanation of the working of this trigger. i have 2 model B fox shotguns with single triggers. the explanation the writer did on the lefever nitro would explain the model b fox trigger workings. the major differences in the two triggers is the cost effective approach the savage company took in designing their single trigger for double guns. from the pictures of the western arms/lefever nitro posted here their single trigger is made of more substantial material ect. same goes for the shotguns. the stevens 311 and model B fox are affordable guns but not made to be shot 60,000 round without considerable wear -- if it lasts that long. the locking system on the lefever nitro are considerable more robust in build and with a steel forged receiver should last about the life of a browning citori before needing a rebuild to move the latch lever well right of center -- again. single trigger lefever nitros are scarce. single trigger stevens and fox model B doubles are more plentiful but still difficult to find. wish i had discovered the lefever nitro about 15-20 years ago. i also found a line drawing of the lefever nitro special single non-selective trigger on this page again by accident. i did move the drawing to my picture storage . i can not repost or copy it to a hard copy. i also saw no way i could post a picture on this page in a reply.
