Complex sentence: This coincides with claims stating the original T1s operated at higher operational speeds than the official recorded speed held by "Mallard" as far back as 1946, but the legitimacy of such claims can't be verified.
Split into simpler sentences: This coincides with claims stating the original T1s operated at higher operational speeds than the official recorded speed held by "Mallard". These claims go as far back as 1946, but the legitimacy of such claims can't be verified.