Ok, I know very little about these so I have a few questions.  

1.  How can you verify if these are pre-ban or not?  Were they even around post ban?  The serial number is 010xx on an MX15A1.  

2.  Do these function well or should you stay away from them.  Of course I would replace the upper, are they small pin or large?

3.  What is a fair price on an very good condition one?

Thanks everyone in advance for your help, I searched back a bit on the board and couldn't find anything helpful.

1--See sellers original dated receipt if he is first owner.

2--High quality part, small pin, lower only holds the mag, trigger group, almost all function is going to be upper.

3--$800 - $1000 if pre-Ban?

Thank you sir!