Ernest Simpson's Reefer/Polo Jacket

Here is Ernest Simpson (as in The Mrs Simpson) in a reefer/polo jacket, displaying coupled buttons of the Coldstream Guards, as a result of his captaincy in the regiment during WWI. Tony Ventresca, of FNB, brought it to my attention. Note the heavy cloth, possibly a barathea; much heavier than the cloth (maybe a serge), that would be used today: