I find it very interesting to see how the numbers looks just slightly different in each country! There has been even time I could see the sender’s country just by looking at the numbers (well, of course the country ID is right there too, but you know)
I am afraid I might be the one sending unclear ID numbers. I have heard many times that my 4 looks a lot like 9. I try to be more careful when writing addresses and ID numbers.
I do my 1 as just a straight single line but 7 has a bar. The straight line 1 might be just me, I think we might have been supposed to do it with a hat at school, but I was too busy for that.
But what I find annoying is when people write the ID next to the address or even have it printed on the same piece of paper. The mailman seems to be annoyed by that too as sometimes the ID number is crossed over if it has been placed right next to the address. That makes the ID very unclear.