The phrase "old hand" is often used to describe someone who is experienced or expert in a particular field. There are many synonyms that can be used to convey a similar meaning, such as veteran, pro, master, guru, seasoned, skilled, knowledgeable, proficient, and adept. Each of these terms could be used to describe someone who has been in a position for a long time and has gained significant expertise. It is important to note that while these synonyms describe someone who is experienced, they may not necessarily convey the same sense of respect or reverence that "old hand" does. Different synonyms may be more or less appropriate depending on the context in which they are used.