9mm Range Officer Question

I found a 9mm Range Officer at the local gun shop today and it was the first time I have handled one.  Lockup and slide/frame fit seemed pretty good, but I noticed a couple of things.  First, they are using a ramped barrel in 9mm.  Nothing wrong with that, but it surprised me.  I couldn't strip it down so I don't know if it was the Clark or Wilson style ramp, but it was a ramp for sure.  

Also, the barrel hood had a vertical slot milled through it that looked to be maybe 20-30 mils wide.  I've fitted quite a few barrels, but never seen one like this.  Anyone know why the slot is there?  K.C., Jerry, somebody...?

The cut in the hood is an empty chamber indicator.
If you can see brass, it is loaded.

Clarence

I thought most all 9mm 1911's used ramped barrels, unlike .45acp.

As Clarence said, it's Springfields loaded chamber indicator.

OK guys, thanks.  Considering the way things crud up I wouldn't think the slot would be a very useful loaded chamber indicator. But that's neither here nor there. Thanks again.