Hello

first of all, make sure your currency is active or not, if not then got to In Currency  

Invoicing ==> Configuration ==> Multi-Currencies ==> Currencies  and make it active.

In odoo v10, Quotation or sales order have currency field, its value is coming when we select customer.
when we select a customer in sales order or quotation, pricelist will automatically come into the sales order,

price list has a currency that will come into a sales order.

based on sales order "currency" symbol will display after and before of the sales amount. 

Thanks