Looks like a fantastic resource. It's interesting re: the joining ages - in my fic I put Archie as joining at 15, trying to strike that balance of education and experience we talked about. If the rule about 3 years' experience was followed strictly that would put him at age 18 in The Even Chance. But then we have Horatio and Jack Hammond seemingly coming straight in to being a M'man. They both had influence behind them -- Horatio's father and Captain Hammond. Bush was unlikely to have had any (I assume; I should finish the books before yapping on), so I would agree that Bush spent time as a seaman first, before moving to the officer line.