Time to put the cuffs on. Henry showed me a cool way to do this called "stotting." The sleeves of a regimental coat in this period should end 1/2" above the wrist joint. This might sound too short, but trust me.
First: pin the under cuff piece to the sleeve opening, making sure the short edges match the lower sleeve seam. Pin the mouth of the sleeve to the long concave edge of the under cuff. The under cuff must be exactly the same size as the sleeve with no overlap. Pin it so the edges of the under cuff are touching (as shown.)
Now comes the fun part. Carefully sew the short edges of the under cuff together. Don't sew it to the sleeve. The cuffs on this coat will fold down to cover the hands in cold weather. This technique keeps the cuff seam from bulking up as layers are added.
If the long, convex, outside edge of the under cuff doesn't match when done, carefully trim it.
The last step is to carefully fold 1/2" of the under cuff into the sleeve, as shown at right, and iron it all the way around. Now the cuff comes right down to the wrist. Next time, the blue over cuff gets added and it becomes a mini lapel: complete with tapes, buttonholes, and buttons.