You mention "123" with the shift down and that in itself gives us a clue about it's possible origins. If the last part was shifted `123` on a UK keyboard then it would be `!"£`. So apart from USA layout keyboards, what other keyboard layouts country wise yeild a the same result from shifted 123. Still does not prove anything, but certainly is something to be mindful of. Either way I know I can sleep at night.
On the other hand, I know several Swedish programmers (here in Sweden) who do programming on a US keyboard. In part because it's more difficult to get the {}[], etc. keys with a Swedish keyboard. I suspect the same might be true with other nationalities.
I will exclude France and Germany if the (Shift-123) is different from French/German layout, but otherwise a lot of programmers (power users) use the US layout. Esp. if we are speaking about people of certain age who maybe have started when DOS was cool.
