Don't feel bad... I have a Yamaha 12 string. It's a "FG-410-12" When I enter my serial number it tells me it was made from 1988 until 1998. However I bought mine brand new and still have the receipt for it dated 1973 so their system leaves a lot to be desired. Every ten years they start the numbering system all ove again. Unless you have the org. receipt there may be no way of telling for sure... Good Luck

Hw does a chemical change differ from a physical change? - Google Search

This sounds like a homework question. So here's a link to get you started. Do a little reading, and if you're still not sure, post back what you think the difference might be and we'll help you from there.

A chemical change is when the colour changes or a gas is given off, something that indicates a substance's chemical properties (what it reacts with, how, how many electrons it has, the atomic structure etc) - and in some instances it's name - has changed.

A physical change... well the only way I could describe it is like breaking a china plate. The thing has changed, its broken now, but the material the plate is composed of is the same.