“You simply sew up the seams. Complete accessories with each dress.”
One way women could save a little on dresses during the great Depression was by buying a partially constructed dress and sewing their own hems, side-seams, buttons, etc. I didn’t find much information online about the Berth Robert company, or its rival, Fifth Avenue Modes. But I have encountered a sampling of their ads in nineteen thirties’ magazines.
Just at random, I found this Berth Robert ad in The Delineator, February 1931 issue. I may yet find earlier ones.

Top of ad for Berth Robert Semi-Finished Dress catalog, from The Delineator, Feb. 1931, page 79. “Dress smartly by the Berth Robert Plan and save.”
“In Paris we select the smartest, cleverest styles. Then, in our own New York atelier these charming frocks are tailored to your measurements from the finest fabrics. All difficult sewing — necklines, tailoring, tucking and pleating — is completely, beautifully done. All you do is the easy finishing up. Even an inexperienced sewer can easily finish a Berth Robert Frock or Ensemble.
“This Spring, dress with Parisian smartness, yet actually save money by the Berth Robert Plan.”
The implication is that all the buyer will need is a needle and thread (see pictures.)
This ad, from the Fifth Avenue Modes company, appeared in the same issue of The Delineator:
“How to be well-dressed on a limited budget — that is the problem which the “Finish-at-Home” Plan is solving for so many fashionable women today! Finish-at-Home fashions save you half!”
“Made to Your Order. The dress you select comes from Fifth Avenue Modes cut to your exact size or measurements, with all the difficult work done. . . . Our expert men-tailors complete all the tailoring, pleating, hemstitching, tucking, etc., so that all you have to do is to put together a few completely-made parts. No bothersome patterns to follow, no expense for outside work, no trimmings to buy or make — we furnish everything you need for your dress, down to the spool of matching thread.
“A Little Sewing – A Great Saving. You can easily follow the common-sense finishing instructions we send with your dress. . . . And what you save by this simple sewing will enable you to have two stylish dresses for the usual cost of one ready-made dress of equal style and quality.”
No, both firms don’t have the same mailing address, although they do have very similar ads.
Both companies continued to advertise for several years, in various magazines.
“All you need to do is to sew up a few simple seams . . . fitting the coat or dress perfectly to your figure . . . And presto . . . you have a luxurious spring wardrobe at what the cloth alone would ordinarily cost you. Buying direct from the producer, on the semi-made plan, effects these great savings.”

“Worn with Pride by hundreds of thousands of smart women.” Berth Robert Semi-Made dresses ad, Woman’s Home Companion, Feb. 1936.
“Many women who can afford the finest favor Berth Robert Semi-Made dresses. . . . All you do is sew a few simple seams, adjusting the dress to your figure perfectly as you sew. . . and as you sew you save.”
Fifth Avenue Modes was still in business, too:

“Dress with Fifth Avenue Smartness Yet Save Half!” Finish-Your-Own dress ad, Fifth Avenue Modes, in Woman’s Home Companion, Sept. 1937.
“With our “Finish-at-Home” Plan, your frocks are cut to your own, individual measurements! . . . We furnish all the trimmings and findings . . . you have only a few simple seams to sew! . . . If you want custom-cut clothes and chic accessories, send today for our Magazine of Fashion. FREE!”
There seems to be a link with Betty Wales fashions, too. I’ve seen Betty Wales fashion ads in magazines as early as 1917. But’s that’s another story. . . .
Artfire dot com has pages from a 1939 Fifth Avenue Modes catalog for sale, but there’s no hint of “Finish-Your-Own” that I can see. There is a paragraph about both companies in an article by Madelyn Shaw about the Tirocchi sisters, dressmakers in Providence, which you can read online; click here.
I just found an affordable 1934 Berth Robert catalog at Ebay, so I’m looking forward to finding out more when it arrives. I’m especially looking forward to seeing the size range, and the prices of the semi-finished frocks and coats, which cost “half as much” as comparable finished clothing.