Toronto. Leitz didn’t add factory synchronization until the model IIIf in 1950. However, there were many options for adding a flash gun and synchronization pre IIIf. This particular flash was manufactured for Leitz New York in the mid 1940s. A matt finish in the reflector allowed softer lighting for portrait work.
The flash used batteries and an Edison base bulb or adaptor. The synchronization was accomplished by a custom base plate for a specially modified IIIa camera. The code name for this flash and base is SELSY. The gun is a model VIIIA. Various flash guns were made by Leitz Wetzlar and Leitz New York.
James Lager’s Illustrated History of the Leica, Volume III – Accessories has some wonderful photos of the pre IIIf flash guns and synchronization methods they used.