I've come across some oddball stuff like that. I had an American made wrench that was marked 9/16 but was actually 5/8. I also had some hardware that gave me hard to find problems like a new bolt that looked like it had threads but the grooves didn't climb up the shaft. It had individual grooves that only went around in a circle. Also, a piece of brand new 16 guage copper wire that was broken inside but worked as long as it was straight. Every time I tested the electrical system with a multimeter everything worked including the wire but as soon as I put that wire on and it got a slight bend in it nothing worked. I also had a cast fitting on a fuel return line that looked normal but if you looked inside it was cast shut. It kept causing a brand new fuel injection pump to chatter but the engine still ran.
I think some of this was done as a joke. How does a wrench get mismarked or a bolt get grooves that go no where unless someone purposely puts it there.