By way of contrast, here is a picture of the two main types of Herse stem. On the left is the early version, on a 1946 machine, and on the right the 'modernised' version by Jean Desbois c.1980. They are quite different, but both are beautiful. I just wished that Desbois had continued using the beautiful chamfer-headed screws, rather than allen bolts. The early version had the visible expander bolt head, which was replaced a little later by the concealed expander beneath the name cap, and the stem also has an integral brake cable 'bridge'....see second photo of 1953 machine.
It's mentioned in the Herse book that the stems were made by hand. The holes for the slot were done on a drill press and then four hours of filing later, the stem was complete!! I'm not so sure though - How was the ridge around the handlebar exits made? I think you should have been authentic and carved it by hand...........only joking!!