A friend here in Norway has an Airborne trailer with the perforated spoke type wheel rim, not the split-rim.
He finds that it is German-made. Apparently by a company called Kronprins.
We are wondering whether pre-war civil cars in the UK were fitted with imported rims, and that the split-rim only came in to use once these stocks had been used up.
Any theories, knowledge, data, would be appreciated.