GR with a crown is the cypher of the ruling monarch. The problem is that there has been several ’GR’s since 1774 when Barron took out his patent, and the locks have been more or less continuously made since then finally dyeing out between the wars. (WWI - WWII) Do post a few pictures of the chest and lock, and if possible one of the lock interior when I’m sure a time frame can be suggested.