Old VS New Maglight

Wonder if someone can tell me about my old maglite. It's a 3D and I've just noticed that it has a larger inside diameter than a new 3D Mag LED that I just bought. I can't remember when I got the older one but it's been a long time, maybe 15-20 yrs.
Did they change the design at some point? Ok, obviously they did, but I'm interested in the history so if anyone has some detail about the changes please tell me about it.
The old one seems heavier and better built. Were the design changes an effort to improve or to make "cheaper" light?
Also, will the older one take a Fivemega 12AA to 3D holder without boring it out?.
Thanks

Don't know the history, but the non D prefix mags are bigger bore. I have an old 2d and the sanwich shop 8aa to 2d goes right in with no boring required (using eneloop or elite 1700's). Someone on the board said the bigger bore (old ones) were in the days of paper covered cells to compensate for humidity swelling. Makes sense to me. I used my old 2d to build a mag 64 and it works fine. An added bonus is the host is all dinged up and looks pretty rough, so I get to use it and not worry about a ding or a scratch.

My older one is a little battle weary too but like you I think that that is what makes it cool.
Now does anyone know the timeline of changes to the maglite or can point to a link where I can get that info?