A few Foundation Day Sets (full title: 建国記念日セット, kenkoku kinenbi set) have been released and sold by Movic.
The retail value of each is 1260円 ($16.80).
Second hand, they appear to range from 1000円 ($13.33) to 2500円 ($33.33)
Each set mostly consists of the same items: the packaging is always a white box and clear lid, holding a card on the left, and a charm keychain on the right.
Each card-- officially labelled as a birthday card-- is round, appearing more like a coaster. They're about 90 mm in diameter, feature anime art of the relevant character, and show the month and day of their birthday.
The keychains feature a small collection of charms, measuring about 120 mm from the top of the fastener to the bottom of the lowest charm. One is always the character's flag, while the others may be any items relating to the character.
Both the birthday card and the box itself read "Happy Birthday" in English, which has led to both Japanese and western fandom commonly calling the items "birthday charms" or "birthday sets".
Currently, four of these sets have been made. The characters featured have been America, France, Japan, and Italy. America's charm has two toy soldiers, and both a red and a blue star. France's charm has two Eiffel Towers, and both a red and a white rose. For both America and France, the birthday card features chibi art of them holding their flag.