Late 1920's.
If you're going to provide the gentleman with a new robe for Christmas, this is a good time to settle on a pattern and fabric.
This elegant double-breasted model features two piece coat-style sleeves; both shawl and notched collars; and both welt and patch pockets. View D shows contrasting fabric used for the collar, sleeve cuffs, pocket bands, and tie. The robe can be lined; very brief instructions are given on the layout chart on how to use the pattern pieces to cut the lining.
Yardage is given for 72" wide cloth, with View C of the size 38 robe requiring 2 3/8th yards. This layout means that if the blanket has a wide border, it will appear as a band around the bottom of the robe. Notice from the layout that the front facings will need to be pieced (Personally, I'd probably cut them from a different fabric.)
In 1928 you could purchase a blanket from Montgomery Ward that measured 72" by 84", which would be
just enough, though you might have to shorten the robe by an inch or two.
Instructions are given for lining and interlining the robe, making this a fairly substantial garment.
Made up in wool or satin, and lined with satin, I think this garment needs to be taken more seriously than today's casual terry bath robes, and it is certainly a far cry from today's usual "at-home" wear of sweats and a t-shirt.
Or, if this all seems like too much work, Montgomery Ward also sold Beacon blanket robes, sparing you the work. These still show up on ebay now and again.