Merit medal

Another one of my fob medals. This one is a 1930 Silver cross Merit medal for Physical Exercises awarded to N. Thomson by James Fenton & Co . It is 33mm x 30mm and weighs 9.4 grams. I am interested in another mark found on it: E.S.A London. Any idea what it will stand for? I have seen it on other fobs by them as well.

Merit marks.jpg
Merit front.jpg
Merit back.jpg

ESA is likely to be the retailer and almost certainly stands for Educational Supply Association, a supplier of educational equipment, etc. to schools.

Also thought it must be something to do with education. I like the overall shape of this medal, almost like a German Iron cross.