In possession of a possibly rare board game

After about 20 minutes of Googling, I saw that there's quite a few copies of the game, which is named U-Boat, for sale on places like eBay and Amazon.  I also found a couple of pages here and here that give some information about the creators of the game, as well as some basics on how to play and what the goal of the game is, and that the game had two releases - 1959 and 1961 - with the latter version basically just having a revision of the ruleset.  I also found a PDF of the rules sheet for the 1961 version here.  Finally, the creators of the game, Avalon Hill, are still in business, being a brand under Hasbro, with a website here.  Any other pages I found mentioning the game mostly just had similar information, nothing different from the pages I linked.