Early '69s would be steel and chrome plated.
John, ORIGINAL early 69s would be steel and chrome plated. Many replacements, even some from years ago, would be stainless...when our cars were used as daily drivers, and subjected to this indignation and the inherent road rash, replacing wheel covers was something easy and not too costly to do. Many originals are scratched, rusted on the back, or front--or really in bad shape.
Brian, if you have Chrome plated steel wheel covers, and they are as old as the car (or nearly so), it would be almost impossible NOT to have some manner of rust on the back side. The stainless would be pretty clean, but even they might rust just a tiny bit if neglected. Chrome also has a different "color" than stainless, but unless you have the two side by side it might be hard to describe. Chrome would be a bit warmer in tone.
The photo here shows OEM stainless steel wheel cover on the left, and a reproduction (they are out there...) on the right. It's been discussed before but the OEM is heavier gauge, higher polish, and higher overall quality. The repro is certainly acceptable and carried a lower price.