If old mate has actual untouched brick coke (keep in mind they've been using phenacetin in Columbia very regularly for the past 12 years to bulk up the weight), expect anything from 50 to maybe 79ish 80%>.
Once upon a time I used to get ounces still wrapped in the condom shape cellophane... That shit was absolutely amazing. Tested clear from all cuts, and had me feeling all kinds of incredible. Was still adulterated as it was oily and smelled of diesel (partly because it was smuggled in fucking petrol jerry cans, partly because they use diesel to extract).
If I were you, I'd do an acetone wash and a chloroform wash to get rid of any amphet of phenacetin and/or paracetamol that's found its way into your gear. As always, slow and steady wins the race. Start low, gradually increase. Oh, also... ALWAYS test your gear for fentanyl too. I may be a bit anal with the way I go about using, but at least I know I'm using what I want to be. Nothing worse than racking up and tweaking out like you just shot up a couple points or shard.
Be safe.