Frank posted this video that comments on the older Sonor throws. I have the link set to take you specifically to the topic in question.
According to Rick, in this video, that particular throw off was discontinued somewhere around '78.
Here is a throw on a 14X4" Designer I have from the early run of Designers, and it has a similar throw design. I have included pics of the inside of the shell to demonstrate that this wasn't a throw added later, and to the best of my knowledge, the hole pattern doesn't fit anything else Sonor did or does use.
This thing is actually pretty raggedy. I hope to be able to rehab it, or maybe look for another one somewhere. The drum finish is beautiful. It would be a shame to have to mod the shell for a good throw off.
As to the video, here is a good product for cleaning/lubricating similar type items:
