The OBP LEM is identical to the OFO LEM. Same as the AMO, too.
We all went to the same armorers course and no mention was made of any differences.
The weak point on these is, by far, the trigger rebound spring. I've broken two and seen another 10 or so.
Seen two cracked slides (saw one happen). They both cracked the front part of the slide above the hole where the recoil spring/guide rod pokes through.
I broke my hammer strut at the same time my second trigger rebound spring broke.
These were all high round count guns, somewhere between 7,000 and 10,000 rounds of hot 155 JHP.