PS = Pink Sheets or for a better name it is now called
OTCMARKETS.com, it used to be called PinkSheets.com
This is where the company uploads its quarterly and annual
financials and where any other non-reporting pink sheet companies
upload their financials. When the company decides to uplist
to a higher exchange within the OTCMarkets.com threshold,
either OTCBB, OTCQX or OTCQB, then they will be uploading
forms 10Q (quarterly) and 10K (annually) to the SEC as a fully
reporting company with audited financials signed off on by
an accounting firm. 10Q and 10K are the forms submitted to the
SEC for all fully reporting companies including Apple, Google,
General Electric, etc.
I hope this helps.