That's what I would do. Pop the cover and look at a few chips. They will usually be date coded with YYWW, a 4 digit number, like 8821 or 9716. Sometimes the coding is a little different, but the first two digits are usually the year.
Originally Posted by K8ERV
If you find two or more components with the same year coding, you can be assured that the radio was manufactured during or after that year. Rarely are really old parts used, so the coding will almost always be in the year of manufacture, or possibly the year or two before.
This picture shows a chip with date code 9341:
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