The 445 MBOX is a C3 stepping derived from a Deneb core. The 440 IBOX listed on newegg is a C2 stepping derived from a Propus core. They do make a C3 440 also, that being derived from a Propus core. This taken from info listed on CPU World.
Stepping codes used for Ibox 440: AADHC AD and CADAC AD
Stepping code used for Mbox 440: AADAC AD
Stepping code used for 445: CACAC AC
What is the difference between the two besides the .1 ghz increase.