Will asks...

"What brand is that grip safety?
What is that clearance on the top of the tab for? That is what looks so weird to me. It's been a while since I looked inside a 1911, but I'm drawing a blank. If it hits the frame, then the frame may be out of spec."

With regard to this:

It's a Caspian on the bottom. 

The clearance on the top  of the tab is weird.  And unnecessary for function.  It does make it easier to gunsmith as you can take the part in an out without full disassembly.  That's all.  For beavertails.  Regular grip safeties are already easy on/off if I am not mistaken.  A full size tab only hits the frame when out of position.

There is a LOT of that in gunsmith.  Take the gun apart, fix something, put it back together, check something, take the gun apart, fix something, put it back together....  Ad infinitum.  The clearance is just to make that onerous process moderately easier.

And there is a trick to getting the part in and out that took me an hour to learn on my own.  There is a lit twist and a turn as you are putting it in and out.  Sorta like the acrobatics you need to do to get the bolt and operating rod off of an M14.