It's your floor. You got enough, it's the windshield washer reservoir on the left one I believe.
I really like these little cars, always have since riding my bike down to look at them in the show room floor.
I have an odd story on these little "doors" we are talking about here. I bought a basket case 64 Vette around 1986. The vents on the B pillar were missing. These vents are a pot metal piece with all four of them being different.
So I had found a couple of them, one from each side but still needed the other one, I think it was the bottom ones on each side. One of these Datsun Z cars came into the shop and it had the Vette vents I needed installed on these access doors! I asked about them and the guy said sure, you can have them, replace the doors with ones without the hole and keep the vents. I did just that and got my vents.