And it's another scrap from the past! Tucked in a lovely 1940s pattern from McCall was this scrap of facing:
The fabric is a lovely pink with a hint of peach, and appears to be rayon, rather than silk.
And here is the pattern, a gorgeous fitted slip in day or evening length, with an empire waistline and a marvelous decollete sweetheart neckline. The slip hugs the bodice so well that it has a side zipper closing.
The pattern is annotated with the original seamstress's design changes to the neckline. She seems to have preferred a sweetheart neckline in both back and front, rather than just in front, and higher than the original neckline.