Don’t forget that the trim around the sides is white instead of tan (unless the trim on most 206s yellowed over time) & the bracket’s a different shape.
Oh, Brandy, I’d recommend you replace that detector as it’s well over 10 years old (you’re supposed to replace smoke detectors every 10 years as by then they likely won’t alarm in an actual fire). Since they’re so rare though, don’t throw it away; give it to a collector.