I dont know about IPs but the normal production boats the actual wire is the same. I.e. They dont put in a different wire grid. Just different bits on the ends.
For peace of mind you might pay for some test, because any test you try yourself wont give you that peace of mind.
Remember if you ask a marine
electrician he will tell you to rewire it as he will make thousands. So book one for a test but tell them from the outset, and all the way through, that he will not get an y job from you except for the test he is doing. Then he wont have an ulterior motive