Woodie:
None of the three Leerdam pieces I have are marked, which I was told, is not unusual for the pieces I have. In fact, there was a spikeball example on eBay recently on which somebody had marked T.S., which the seller presumed meant it was designed by Timo Sarpaneva It sold for $149.99.
For one piece I have, I ended up emailing Willem Botterweg, the owner of the gallery mentioned in one of the threads I referred to, and he was very helpful. He is an incredible font of knowledge on Leerdam. His email address is auctions@botterweg.com. Perhaps wait a couple of days to see if anyone else suggests a maker and then try him.
Good luck.
David