I'd think it's at least 100 years old. Ammonia fumed quarter sawn oak gain popularity at the end of the 19th century and fell out of favor by the second quarter of the 20th century. It really reached it zenith in the early 20's. They were still making that kind of stuff in the 40's but it was stylistically much different and would likely have been made of walnut as opposed to oak as it was more fashionable.
This is of course all just based on theory, without a makers mark or label its nearly impossible to put a specific date on something like that. If your shipping was 30% of what you paid for it, I'd say you did pretty well. Now just look it over and find that Gustav Stickley mark.
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