That is the battery tray on the bottom of the toy car. I didn't know that D batteries were 1.5v. I guess that's how they were noted in Japan back in the 50/60's
Zep, that toy is in like new inside! It's worth finding out what it's worth; I'd think hundreds at least. iirc, the one I saw 30 years ago went for 450. It wasn't that good.