I'm afraid we can rule out Malcolm Rouchhead as the original Malcolm Donaldson. I found his death registration on Scotland's People. He died in 1940 and his name is given as "John Jarvie formerly Malcolm Roughhead; Coal Miner (retired); Single. Mother: "Margaret Roughhead, Cotton Weaver, afterwards married to Thomas Jarvie". (I suspect this was a common law marriage as I can't find a marriage registration for them).
Back to the hunt!