Hello. I have this 12 gauge with serial number N765XXX. Does anyone know if this number is from the 1968-72 production or the later 80's/90's? I just want to get an idea of its age. I know it's not worth much and people have strong opinions against this model, but I happen to like mine. I'm not interested in one's personal opinion about the quality of the Model 1400, just info on the serial number. Thank you in advance for any such info.