Hi Sport45! Thanks for your thoughts. You are most likely right about all Marlins having cross bolt safeties by 1984. They started adding this "safety" in 1983. No, my Marlin does not have a screw or anything where a cross bolt safety was removed. It never had one. This nixes the idea it was made in 1988 or 1989!
It had to be made prior to 1984. I just can't find any chart that works with this rifle my friends father hunted with! I will try to contact Marlin tomorrow and see what they say. Thanks again! Ken