I couldn't find the specific origin of the phrase, "He's lost his marbles." However, at least one source quoted a newspaper article in which the phrase was used in the late 1800's. The phrase may be old, but marbles are ancient.
Marbles were found in the tombs of ancient Egyptians. My father played marbles in his youth (he wasn't Egyptian), but I never learned any of the games. Still, I had marbles, and I thought they were fascinating. Four of the marbles above are called "cat's eyes," because of the different colored vanes inside. The blue marble, which is mostly transparent, is called a "cleary." The large red one above was used by my wife, Peggy, as a "shooter" when she played marbles many years ago.
Although you can buy an inexpensive bag of marbles at many toy stores, there are artists who make "fine art marbles." They are beautiful, and expensive.
In support of marbles aficionados, there exists the IAMC, or "International Association of Marble Collectors." Their annual convention will be held this coming October in Las Vegas, Nevada. The National Marbles Tournament is a 501(c)(3) organization that has sponsored an annual tournament since 1922. There are many more.
A quick search on eBay for "rare marbles" resulted in 4,885 listings. On the first page alone, I saw marbles priced from $.99 to $2499!
Nicks in the marbles give them age and character. Peggy's shooter is pretty scuffed up from time spent clobbering other marbles and bouncing around in the dirt of her backyard. The marbles reflect each other. The nicks also pick up different colors.
Marbles are beautiful, and they have given many of us an opportunity to play. Beauty and play are gifts we can all enjoy.