That's a very interesting mic on the MCS looks like a Jedi series mic
I was going to say the same... I've seen them around a few times, but have never seen them in use. I know that you can swap out the back lapel clips for those discs used for mic-hang ups, I think that's how they do it with the FDNY slings.
Overall, this install is awesome. Your attention to detail is amazing. Especially fitting the rockers into the factory switches!!!