The patch can be obtained from the Internet Archives. Download: https://archive.org/details/SS2V3_ZIP

1) The historical data in the initial Halls of Fame reflects postwar JANAC

  tonnage scores analysis with one exception: the War Career lists, which
  represent wartime claims. We used these because they seemed more in the
  spirit of the game. The top ten tonnage scores for war careers per JANAC
  are: Fluckey(95,360), O'Kane(93,824), Underwood(75,386), Cutter(72,000),
  Munson(67,630), Gross(65,735), Whitaker(60,846), Reich (59,839), 
  Triebel(58,837), Andrews(57,243), Morton(55,000).

2) Fans of strict historical accuracy have noted that contacts are more

  frequent in Silent Service II than in real life. In reality many subs
  never found a target throughout an entire war patrol. To play the 
  simulation as a "purist", use a deck of cards. For each contact you make
  where there's an option to avoid battle (you have a Y/N choice), draw a
  card. If the card is 2 through 10, or an Ace, you MUST say no (N). If you 
  get royalty (K,Q or J) you can make the choice normally. Reshuffle 
  after every patrol.

-- SILENT SERVICE II IBM Version 457.03, 02/10/91 -- Historical notes above, playing notes below.

3) NEW KEY: The "s" key toggles on and off a special "extra-slow" speed.

  This may be useful on 386/33+ or 486 machines. The slow-down affects ALL
  time acceleration modes, not just the slowest.

4) NEW KEY: The "l" (lower-case L) key spins the periscope 180 degrees.

5) You can restore the original historical data to your various Hall of Fame

  screens by copying the HALL.??? files from Disk C.

6) Make sure CapsLock is OFF when you play. We also suggest having NumLock

  off unless your keyboard requires it to be on for functional cursor keys.

7) Ignore the "not enough memory" warning at your peril. The alt F1 key will

  report currently available RAM. If you have 0 or a small number (like 3!)
  you're cruising for a crash. See the Technical Supplement for details.
  SSII isn't the only game that needs lots of memory, especially in DOS 4.
  I (Arnold Hendrick) have a BAT file that lets me select one of six 
  different configurations (Config.Sys and Autoexec.Bat) for my DOS 4.01
  386/20, depending on the memory and type of drivers a game requires.

8) Your current save game and Hall of Fame files can not be used with the

  457.03 version of SSII. There have been changes to these files and the 
  way that they are saved. This was to repair several bugs found with 
  restoring the game from saved as well as the Hall of Fame.

Topic on Talk:Silent Service II