Spaceship One Question

I was at the Smithsonian Museum (the Air and Space one in Washingtion
D.C.) last weekend, where Spaceship One hangs in the lobby. Does
anybody know why there is a dent in the bottom of the fuselage, very
close to the back? I wonder if I missed something in the press releases
or other coverage. There are bits of online literature that acknowledge
but don't explain the dent.

Great museum, by the way, both of them in fact (the other one is close
to Dulles airport). I'm preaching to the choir here