Au fait and Oldtimer

Au fait adjective - Being up to particular standard or level especially in being up to date in knowledge.

Oldtimer and au fait are semantically related In some cases you can replace term "Oldtimer" with "Au fait", this terms are similar.

Oldtimer noun - An experienced person who has been through many battles; someone who has given long service.

Au fait and oldtimer are semantically related in able to perform topic. Sometimes you can use "Au fait" instead an adjective "Oldtimer".