Mysterious 1950s shoes--what do you think?

I have this pair of ankle strap sandals that I was preparing to list on my website, and then I noticed something unusual about them. (How I missed it while I was photographing them is weird--must have been really focused that day, LOL!)

I believe that they date from the mid-to-late 1950s. But what is unusual, at least in my experience, is that the ankle straps only attach on one side of the sole. Nothing appears to be missing or damaged--no signs of a strap having been removed from the other side, that I can see. So, what do you shoe experts out there think? Is this more common than I am aware of? TIA!

 

I have seen this before, but its not common. The shoes are mid 50s 53-55ish

 

Thanks for your (always valuable!) input, Jonathan!

I wanted to make sure that it wasn’t some kind of manufacturing flaw. Knowing that there are other shoes out there like this makes me feel better about listing them for sale.

 

Beautiful shoes, Amy!