Probably UK, number doesn't seem right for US. Too old to check via online DB. Suba-Seal the trademark seems to belong to William Freeman Ltd of Barnsley, Yorkshire,
"Class 21:Small domestic utensils and containers (not of precious metal or coated therewith); kneeling pads for domestic use; draining boards and hot water bottles."
There are other rubber applications, mostly by the same company. First filled as a trademark in 1966 and still current