40 bucks in 1919 is 2 ounces of gold worth about $2,300 There was no way to invest in the S&P500 back in 1919. There was no index funds in 1919 and most investment funds went belly up in 1929. This invest in KO is not what people were investing in, it is what Warren Buffet states to make himself look good because he has held it for a long long time, however he has not done people any favors in getting them to buy KO as he continually touts it from 1999, the stock has paid dividends and that is about it. Since it was a new unknown issue in 1919 is Warren actually advocating today people should put $3,000 (6% of annual income) into every new issue on the NYSE in hopes by 2199 will have equivalent of 10 million for heirs? How many new issues should be invested in 273 came out in 2014 to invest the equivalent of $40 in 1919 in every new issue would require $673,00 should I plan on that each year as an investment plan? Or just pick one and hope it's a winner? Popular in 1919 was General Motors, Pierce Arrow, Stutz, Texaco, Pennsylvania Railroad and Central Leather. Stutz and Pierce being two new stocks in the upcoming auto industry (didn't quite make it). Some stocks would have gotten you rich many went belly up.
It is always nice to be able to pick your investments 90 years after the fact as Warren does. Charlie Munger does a nice job selecting stocks on an ongoing basis and has an eye for long term potential.
Gold is really just cash hedge that holds it's value against inflation long term with major fluctuations. It has a real purpose in a portfolio, but yes owning it probably lessens the chance of maximum wealth as it is a defensive asset not an offensive one.