I have one of these as well (imagine that :rolleyes:)). What I'm curious about is whether yours is silver or as it looks in natural light photos - goldish?
I got mine about a year ago from a certain seller we all know and wish his prices were accurate regarding our own stuff. Even though he is notoriously high on his prices, I paid about $30 for it, which means that it is probably worth about $20.
I seldom see one of these for sale or even listed as a photo somewhere, so on that basis alone, I'd say it is not common. However, it was produced by the LMD at such a point in time that probably only a small number were ever issued before the end of the SU. Obviously, they minted way more of these aluminum badges with a cloth insert on the suspension, than were given to specific criminal investigators.
If you find one with a serial number, then you are probably talking about around $100, but like this - $25-30.
As for the classic all-seeing "pyramid's eye" - that's another question. I may have what Igor wrote about it and if so I'll find it and post it, but I need to get some sleep now.
Remaining photos. I just noticed that though I said "pyramid's eye," it is clearly placed within a pentagon - another mystical symbol - and another mystery that's too late tonight to tackle.:)