1950's Slab Foundation?

[Richard A. Hetzel]

Normally can see slab along exterior wall.

Normally, you should never be able to see the slab along the exterior wall. The proper way to build a slab is to keep it entirely within the foundation, unless it is a monolithic pour with the stem walls, and then you still won't see it. If there is no means of access to a basement or crawl space, it's a pretty safe bet to be a slab on ground.