I've just tried identifying the Leica font using DTD's 'Identifont' website. The closest offering it puts up is a font called 'Malmo Sans'.
Go here to see if you agree:
Identifont - Malm Sans. Failing that Identifont also offers 'Bosis' (which is pretty close, but not quite and also 'Battersea'.
None are spot on however. I tend to agree with earlier posters - its probably a variation on a standard font, but unique to Leica.