These were found at a coast battery site which housed two 6" naval guns up until the 1950s. They seem to be WW2 dated and I have always assumed that they are perhaps crates for the projectiles for the guns, with the little recess around the inside for the drive band, but I have not seen anything like these anywhere before. They are octagonal in section with internal dia 7¼" and height 28". Could anyone enlighten me. Thanks.