Old Tandems - Scot or otherwise can be particularly difficult to date. This one is definitely pre-war (post-war they seem to have used the same numbering sequence as solo machines) with a number 'T19418' - Using the same method of identifying solo machines from this era, the '8' at the end would represent 1938 but would give a frame number 1941 - a bit on the high side for Rattrays annual frame production. Or it could be the 8th frame in 1941. Problem with that is that it's unclear yet wether Rattrays gave up frame production entirely during the war years. Either way, it's a good and original example of a pre-war Scot tandem.