A little "economic intelligence hack".
How to estimate the sales of an competitor using its own website ?
A lot of techies are implemeting, like in Magento 2 for example, an invoice system with a classic table where there is an ID of the invoice.
This ID is , for techie guy, an INT(11) with a primary key and auto increment capabilities.
Then the first sell, will have an invoice with ID 1, the second with ID 2.
The default template gives back the ID for the client.