Copying that wouldn't be difficult at all - it's a very simple pattern. However, that isn't the point, the fabric may be from Gallenga, but the dress is not, and when I suggested it was remade, I wasn't suggesting there had been an alteration - I think someone has unpicked an older dress, laid it out and recut and sewn a new dress from the yardage. In the process of remaking the dress, the signature was cut off, and the resulting dress uses a seam along the lowered waist that is very untypical of Gallenga.
I think you could say this was a late 1920s dress likely made from Gallenga material, and show the side by side images of the labelled Gallenga dress material (you should ask Linda Ames for permission to use the close-up, or direct buyers with a link to that page). However, saying the dress is a Gallenga would be untrue.