Before I comment, I know that there is not enough examples to draw a conclusion. What transition was done first? Did they change the engraved star and date to stamped or did they switch the 90 degree gas port to 45 first? Like the switch from spike to blade, it was documented as a time frame or until they ran out. With the change about 45 gas port or engraved cover nobody knows for sure. Something to ponder. Also looking at Matt's 50, I had at first look, thought that his carrier showed a Q on it. But when I looked closer it is actually a faulty stuck stamp. It is actually 8 8. This would match the bolt. Still no idea about the Q stamp on my other 50.