Two 15-cwt rims I picked up recently have American made “Kant Slip” 9.00-16 W /|\ D tyres FOR BRITISH WHEELS made by Kelly Springfield Tyre Co. on them.
They are a proper NDMS bar grip, and not a retread. I have not been able to find a date on them. The American Kelly-Springfield Tire Company was founded in 1894. It was acquired in 1935 by the Goodyear Tire and Rubber Company, who maintained it as a subsidiary until 1999 when it was integrated into Goodyear North America. It continues today as a major brand under Goodyear. So they could have been made anytime during the past.
Could it be the US supplied tyres for British wheels under Lend-Lease? Or would the US supply European MDAP recipients after WW2 with tyres made for their ex-Canadian equipment?