The commonly found engraved keychains are those of coins of a particular country. These in fact are sold as souvenirs. These may not be authentic coins, but are minted to be sold as tourist gifts. They may carry the engraving of a popular historic figure or monument of that country. It could also be an engraving of the flag or the map of the country and on the other side the year of visit. These souvenirs need not be in the shape of a coin, but could be square or rectangular, or for that matter any other shape.
In India, you can generally avail of engraved keychains carrying idols of the gods and goddesses. During the festival of Diwali, people generally present one another with silver engraved keychains. These generally carry the engraving of goddess Lakshmi, the elephant god Ganesh, the swastika or the symbol of Om.
There is a wide range of keychains with engravings to select from, however, you could also design your own keychain and have something personal engraved. This could be a special message, a face, an object, etc. You could gift someone a keychain with their portrait engraved on it. If not that you could get their favorite bird, animal, object, flower, etc engraved.
If you know somebody is a fan of a particular film star or sportsperson, you could get their portrait engraved and gift them the keychain. It will surely add to their movie memorabilia, making them happier than you could have ever imagined.
These keychains are generally considered antique and archaic, simply because this was a common type of keychain in eras gone by. During those days the keychains generally had engravings of the kings and queens who ruled over that region. Or then such keychains were generally manufactured to commemorate a particular personality or event. This trend does continue even today. For instance, during the year of the Olympic games, special keychains with engravings are manufactured as a token of memory for this grand event.