I just purchased my first fd and the previos owner said it was rebuilt 10k ago but for the price i purchased with no paperwork . So I went to do oil change and noticed the front cover had NEWER black marker writting near crank. my questions is if this is really rebuilt by mazda or is there a way to tell if it has been rebuilt???

 

Reman motors from Mazda have a ~2"x2" blue plate on the front of the motor near the area of the power steering pump.

What you really want to do is have a compression test done. I'd recommend taking it to IRP in Clifton, NJ for a compression test and general review of the car.