Oh, come on... Isn't this common sense? You're always supposed to put the currency symbol before the value. Let me explain why.
Lets say someone writes a will/check to give Dinky 50 Dollars. And in the document it is written as "50.00$."
Then, Dinky can easily change the value by editing the document and scratching in 1000 after the 50.00$ and claim he is entitled to "100050.00$."
This couldn't be done if the symbol came before the value "$50.00."
This is only true if you wrote the cent value as well. If you didn't, you can easily forge the value when the symbol is before the amount, i.e.:
"$50" becomes "$50000".