I think this might be what you have seen::

"The HTTP 402 Payment Required is a nonstandard response status code that is reserved for future use. This status code was created to enable digital cash or (micro) payment systems and would indicate that the requested content is not available until the client makes a payment."

https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/402

Can't find where the original source is but it might be from the W3C when HTTP protocols were getting standardised.