RHS Usherette Construction Plans

Because there are only a handful of photos of Patricia Quinn's usherette dress, a lot of information will have to be based on secondary sources and best guesses. 
-  The back of the dress is completely unknown to me.
-  The waist style of the dress is very hard to discern.

-  The lower front pockets are hidden.

What I'm using to supplement these features:

-  Later usherette dresses that were also designed by Sue Blane.
-  Similar historical garments.

-  Design standards that make the most sense. 

I want to start with the midriff segment. It's much more visible on Jaimie Donnelly's usherette dress, but that doesn't mean Quinn's was the same.  However, I believe I can see evidence of it on Quinn's. Additionally, it was a very common feature in mid-century usherette & waitress uniforms.  They both have a thin, black belt (photos from https://www.ozrockyhorror.com). The biggest differences I can see between these two dresses is the button placements, and Donnelly's sleeve caps.

Here's what some other mid-century uniforms with midriff sections looked like:

Next is the back of her dress. All I can really say about that is if a design has a yoke in the front, it very likely will have a yoke in the back.  And below that yoke will have either some pleats or gathers.  That's just standard design practice that I wouldn't deviate from without evidence otherwise.

And finally the pockets. I mean, I can clearly see the bottom of the pocket seams above the hem, but I can't make out the top shaping at all.  It could be flat across the top. It could be scalloped up into midriff. There's just no way to know.

It's entirely possible this dress was purchased at a resale shop, or otherwise already on hand in the theater's storage. This is a common way of costuming low budget productions:  not everything is made from scratch.