The actual date is in a date code on the inside of the guitar. You would have to remove the strings and use a flashlight and your cell phone camera to find it. That's actually the most important part of what I'm looking for. Relating the sequential serial numbers to the date codes. It will probably be 45.??.??, with 45 being the year 1970, and the ? being the month and day. By what data I have your FG-180 was made mid 1970. The FG-140 would be late 1970. If you could find those date codes I'd really appreciate it.