It is Shift+3 within a message for Mac.
It is the same in the inbox as well  


You must move to the message with j/k  
Select a message with x
Then press Shift+3


It could be that your keyboard layout is different.
Using a UK layout, it would be Option + 3 : ⌥ + 3, but this does not work (Not sure why).
You can also remap your keys with the Google Labs feature : Custom keyboard shortcuts

Google Mail Keyboard Shortcut for delete on Mac
I bought a Motobécane last year (pics below), and now that the bottom bracket is broken, I really need to know the model of the bike, to help me change that piece.

It would also be helpful if someone could redirect me to the Motobécane catalogs of the years 82, 83, I can't find them, and I suspect my bike is from this period.

Technical specifications:


frame color: green and black (How customizable was that? I think they didn't sell the same colors each year)
frame: tubing inexternal 707, "trainer" (I don't find the appropriate info about it)
brakes: Weinmann
derailleur: Sachs - Huret. 12 gears
Wheel: Maillard
Bottom Crank: ?? width of the shell: 74mm. From this page http://sheldonbrown.com/vrbn-g-n.html, the old french ones have special dimensions. Also on Motobécane, they are swiss type (left-threaded). I don't know if this is a cotterless one, shimano octalink, or if I can put something more standard?


[EDIT: As suggested by @Blam, I took the bottom bracket out.
First mistake: shell width doesn't correspond to the red line on the pic, but less, so width should be 68mm, I'll double check on the bike.
The Brand is Stronglight, french brand, but the threading is the normal one (left-threaded on the right side, and right-threaded on the left side).
The axle is 120mm long, tapered square. Like this model: http://www.ebay.com/itm/VP-Components-Bottom-Bracket-120mm-Square-Taper-Unsealed-Bike-NEW-/311359596201?pt=LH_DefaultDomain_0&amp;hash=item487e7a66a9

But anyway, I'm still interested in knowing the model of this bike, and/or finding the Motobécane catalogues of years 1982-83]

Important Note: The rear wheel is not the original (was broken). I also changed the part of the crank where I put the feet when I bought it (maybe I shouldn't have...). 

Sorry if it looks quite dirty, I didn't have time to clean.

Pics:











