Quoted:
Thanks for all the info gentleman. It came from one of my fellow Lieutenants at the station. He thought it might be an Olympic Arms but didn't really know. Will the SP1 BCG function fine in place of a SA one for my M&P15? Might keep as a spare if so, otherwise might look to trade it for something else. Appreciate the info none the less.
I would take advantage of the market right now and sell it if I were in your shoes... It does not look bad or very used/abused at all and you could get a good price for it.
When things calm down you take the money you got from selling this and go buy a good FA bolt carrier group. You want a carrier that has not been all hacked up like the one you have here. You would be 'upgrading' at a later date for less money.
I worry less about the weight missing from the back of the carrier as I do the unshrouded firing pin. That mess just bothers me!