2.25*2.25 = 5.0625
3.75*3.75 = 14.0625
5.0625 + 14.0625 = 19.125
sqrt(19.125) ~ 4.373
you could put a 4.3 inch screen in if it had the same aspect ratio...

more reasonable:
4:3 screen
2.125/3 ~ 71%
71% * 4 ~2.83
2.83*2.83 ~ 8
2.125*2.125 ~ 4.51
8 + 4.51 = 12.51
sqrt(12.51) ~ 3.53
Using your measurements,
you could probably squeeze a 3.5 inch 4:3 screen in the tin..
I would be a bit worried about where the backlight is, though.
edit: DAMNIT BUD! :/
for fun, 16:9 screen:
3.5/16 = 21.875%
21.875%*9 = 1.96875
1.96875*1.96875 ~ 3.876
3.5*3.5 = 12.25
3.876+12.25 = 16.126
sqrt(16.126) ~ 4.0157
You could fit up to a 4 inch 16:9 screen in the tin.The metal bits outside the screen shouldn't give you much of a hard time on this one.
I kinda want to build an altoids tin test screen, now...
_________________
ShockSlayer wrote:
Geb's a wild and crazy dude. I can tell, only the most adventurous people keep the hotsauce next to the deodorant.