Question: Can I use this to connect a flash unit to the Leica M3?
Answer: Yes, the Kaiser 1301 flash adapter for center contact can be used to connect a flash unit to a Leica M3. The Leica M3 does not have a built-in hot shoe, but rather a center or PC sync port. With this adapter, you can connect a modern flash unit with a center contact to the camera's sync port. However, please note that only manual flash is possible with the Leica M3 – automatic TTL control is not supported by the camera.