It is easy to get confused, as there was a bustle era..

… then no bustle (“Natural Form”) and then bustles again.  During all the times, ALL fashion aimed for the same silhouettes.   That makes it hard for us today to determine which is which, since a tailored walking dress or riding suit of 1879 would have the same features, design, and construction, but might look completely different than a ball gown.

Whenever defining a date of an ensemble.  Look for the construction.  In this we look for the structured long bodice through the waist and down to the knees with a single vertical paneled seaming – regardless of whether it is split as with a riding jacket, or full as with a ball gown.

(Sketches: 1880 walking dress vs theater ensemble)