Hi Eddi, some days ago I started to dismantle the engine. I found the timing end with a radial oil groove, but interrupted about 10 degrees, I guess.
My first conclusions were wrong. After reassembling the crankcase the first time, I wanted to check lubrication. First, I found the lubrication blocked. I was not able to press any oil from the oilpump to the main bearings. Having rotated the crankshaft a little bit, oil reached both main bearings without any problem. That's the reason I thought a radial oil groove is missing.
On the photo, you can see the extra groove going to the front, you mentioned. As John Mark in his manual recommended, I asked alpha bearings to block this groove when fixing the crankshaft.
After all, dismanteling was really unnecessary. With a little more care, I could have avoided that. But, after all, I enjoyed working on the Douglas again. Thank you for your hints.