IP stock?

I don't own the Carbine Club newsletters so I don't know the history, and stocks are not my forte'. So what makes this an IP stock as advertised on ebay? Thought they were just Robert Irwin made replacement pieces similar to LW or J stamped stocks were and those being by other manufacturers?

M1 Carbine IP Stock | eBay

You are correct. I should have put IP marked stock.

IR-IP stocks are on my two IP carbines. Guessing IR and IP was using up extra wood.

think what makes the ebay one an IP stock is the creative writing....