I've seen many many books and articles (including this Forbes article) claiming Pepsi Co. first started giving out 18k gold watches for retirees in the 40's because "you gave us your time, now we are giving you ours". However I have not seen any actual sources on this claim (and you'd think Pepsi Co would say it somewhere on their website too). I remember seeing this video promoting Social Security program from the 30's with an old man looking at his gold pocket watch engraved with "Thank You For Your Service", but I can't seem to find it right now, so it's very likely that it started earlier than the 40's.