Ilfospeed was Ilfords graded RC paper. Not sure if they've stopped making it, however havn't seen any on shelves for many years, and if it's really 10x10" then never seen any of that one. You'd be best to test it for fog before wasting lots of time on aprint that will never be right. I'd cut a sheet into a few pieces and fix one without it going near the developer, put another in some developer then fix without going near an enlarger. If they are both the same 'whiteness', try one under the enlarger.