Thanks , I would appreciate it. Take care of yourself..Hard to tell by serial # with Bobcat however the 743 was released in 1981 and you are in the first serial number release range, I would guess 1982 or 1983. I do have a source I can find out for sure next week unless someone else knows for sure.
on my old 643, the year, along with a signature was hand scratched into the hydro/fuel tank, i forget which side. i no longer have the machine anymore. i believe mine was an 86. i assume it was a quality control marking.Thanks , I would appreciate it. Take care of yourself..