I thought so.
You can still get something similar on E Bore. I think from Russia. They are of course illegal.
Despite the interesting and helpful comments on this thread, I still think that the origin of the diabolo in 1905-08 remains a bit of a mystery to me.
We can hypothesise (with some certainty) that someone invented them, and that they proved well suited to the LJ/BSA and the Bonehill Anglo Sure-Shot. But were the rifles and the pellets invented separately, or was there some connection?
Probably a happy coincidence. Just a pity we (I) can’t be sure.