[meteorite-list] weathering - from the inside out

[Phil Morgan]

I've always found it curious that many heavily-weathered small stone
NWA meteorites seem to be most altered at the center.

For example, I've posted a photo showing one where the metal in the
interior has completely weathered away.
http://i25.photobucket.com/albums/c57/pkmorgan/postingpics/whatisit.jpg

Can someone explain the processes behind this in a nutshell?

This is a classified meteorite - anyone want to guess which one or at
least the type?

Happy Friday and Best Regards,
Phil