After consulting the sizing chart, I saw I was the size 12, so I bought the size 12/14 pattern. I noticed when I cut it out that there isn't a choice to cut a 12 or 14. There's just one set of cutting lines with a 1/2" seam allowance. I scoured the pattern directions looking to see what seam allowance produced the size 12 measurements.
Finally I wrote to Burnley & Trowbridge to ask. They wrote back the same day, and said that Sharon just made one size for the 12/14 and that the size 12 would fit "comfortably" and the size 14 "just". She advised I make a mockup and see what works for me. Sound advice!
I'm impatient and just want to jump into making the garment, so making a mock up is something I always avoid and always regret having avoided. So this morning I made a mock up of the jacket, and then realized that without the corset, shirt, and vest on, I really have no idea if it fits. Looks like I need a mock up of the vest, too.
Before I came to my senses and did a mock up, I admit I'd already cut out the fashion fabric and flatlined it with cotton canvas, but I haven't sewn any of it together yet, so I can still make adjustments to the pieces before I sew them together. Hey, I'm getting better! LOL!
*edit* Well, I cut out the waistcoat, and it seems to be several inches too big. I had this problem with the Wingeo #410 jacket pattern, too. All the extra ease from a company producing historic patterns, not costumes, strikes me as odd.