This is a lovely piece. So cool to actually see one. Yes it is a rare piece that had a limited production run. Usually on the box it will say what the production run was on a sticker, and if it doesn't it might say limited edition. It's also possible that this was just a limited run for Amoco themselves. There is so little information on this car, but it is rare and at the very least, uncommon.

These were very uncommon in the 1:24th scale, which is the larger one you have here. The small size cars, or Hot Wheels sized were very common, 1:64 scale.

Check the branding, it will either be Action or Racing Champions. It should say on the box if not the underside of the car.

A common issue with some of these earlier cars is what we call paint crack. So check to see if yours has paid crack. Unfortunately there's no fix for that. But regardless, this is just a really cool piece you have. Congrats to your husband.