[Steven Tyler]

I was not taught to add a horizontal line thru my “7”.
My parents, and later older European co-workers, always added this line to their “7”

[Think free or die]

"I was not taught to add a horizontal line thru my “7”. My parents, and later older European co-workers, always added this line to their “7”"
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I was taught this method in my 1970's era German classes. My parents are from what is now the Czech Republic, and they and my grandparents all use(d) the slash. It's indeed European practice, and very well established. My grandparents were born in ~the 1890's.