I can actually check it for you before the trade I think, while both our parties are shown I can do the IV check while checking your Magikarp's summary. Not 100% sure about this, but I think I've done it before.
By the way, I am kinda picky about the mons I take, so I'm really sorry but if it isn't perfect I don't really want it :\ I'm paranoid about seeing a flawless one later and regretting this one...