B-25 question...

Bit of a simple question this, but I came across a B-25 picture posted in
a.b.p.a. (Briefing Time Read PA MAAM). It shows the raised panel ahead of
the cockpit common to all (?) B-25s...



I wondered if anyone could explain what it's function was. Is that armour to
protect the crew, and if so was it added at a later date as some kind of
field mod? Else if it was designed into the aircraft from day one, why does
it protrude/what is it?



Cheers,

Jim Doyle