Niels Jonassen sent the following information about the wooden wheels supplied as factory equipment used on the s.4 to s.6 B20s, and all the B24s:
"These wheels were made by Pagliani e Provenzale from Torino. They usually made golf clubs and billiard cues, and have also been mentioned as producers of 3 wheeled bikes for small children. They existed until a few years ago, but now seem to have disappeared. Without knowing for sure, its possible that P&P also made the wheels for the sports racers as well as the D50. Apart from the centre boss they are very close to the ones on the B20s."
There were also wooden wheels supplied by Nardi, but these are generally understood as after-market equipment.