I got McCall 6617, a very nice and very wearable 1946 blouse pattern, with another pattern, as a giveaway because it's missing a piece.
It turns out that it's missing the entire front. Sigh. Of course it couldn't be a facing or a sleeve band or some other easily-reproduced bit, right.
This gives me an excuse to try scaling up a new pattern piece from the line drawing on the back of the packet. I don't expect this to work flawlessly, but I hope it gets me closer than just trying to redraw it freehand.
I'm using the back bodice piece for scale since I have it and can compare it to the drawing, and it has a convenient and easily-measured straight line down the center back where it would be cut on the fold.
I am assuming a size 16 since that would be mid-range and is the size pattern catalogs used to estimate yardage. Arbitrary, less, but one has to start somewhere.
The copier I have on hand only goes up to 400% so I had to scale up in stages. I scaled up and then measured. The center-to-underarm horizontal measure came out to two inches, which was convenient since the pattern at full size would have been 11 inches (my piece is 10 1/2 inches but it's a bust 32. A bust 34 could safely be estimated to be about a half-inch larger horizontally).
One I got it scaled up to four inches across the underarm, I had to cut it into sections to fit on the copier.
I copied each section individually at 275%, then cut out and taped the pieces together.
It's too long, and shallow across the lower armscye, but it's at least ballpark. I think I can use this method on the blouse front, assuming I expect to do some fitting muslins.