Some of the 60s model Raleigh 3-speeds that were lower in the hierarchy used Dunlop rims with a smooth profile. That your dad's bike ended up with mismatched rims could have happened at the dealer or was a replacement or something along those lines. At any rate, Raleigh certainly did equip bikes with those non-Raleigh pattern rims in that era (and Raleigh-owned and slightly lower end brands used them as well).
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