From the manual (TM-181; 1st printing):

Table 1-1 Game Option Settings
(Settings of 8-Toggle Switch on Space Duel game PCB at D4)
 8   7   6   5   4   3   2   1       Option
On  Off                         3 ships per game
Off Off                         4 ships per game $
On  On                          5 ships per game
Off On                          6 ships per game
        On  Off                *Easy game difficulty
        Off Off                 Normal game difficulty $
        On  On                  Medium game difficulty
        Off On                  Hard game difficulty
                Off Off         English $
                On  Off         German
                On  On          Spanish
                Off On          French
                                Bonus life granted every:
                        Off On  8,000 points
                        Off Off 10,000 points
                        On  Off 15,000 points
                        On  On  No bonus life

$Manufacturer's suggested settings
*Easy-In the beginning of the first wave, 3 targets appear on the
screen.  Targets increase by one in each new wave.
Normal-Space station action is the same as 'Easy'.  Fighter action has
4 targets in the beginning of the first wave.  Targets increase by 2
in each new wave.  Targets move faster and more targets enter.
Medium and Hard-In the beginning of the first wave, 4 targets appear
on the screen.  Targets increase by 2 in each new wave.  As difficulty
increases, targets move faster, and more targets enter.


Table 1-2 Game Price Options
(Settings of 8-Toggle Switch on Space Duel game PCB at B4)
 8   7   6   5   4   3   2   1       Option
Off On                          Free play
Off Off                        *1 coin for 1 game (or 1 player) $
On  On                          1 coin for 2 game (or 2 players)
On  Off                         2 coins for 1 game (or 1 player)
        Off Off                 Right coin mech x 1 $
        On  Off                 Right coin mech x 4
        Off On                  Right coin mech x 5
        On  On                  Right coin mech x 6
                Off             Left coin mech x 1 $
                On              Left coin mech x 2
                    Off Off Off No bonus coins $
                    Off On  Off For every 4 coins, game logic adds 1 more coin
                    On  On  Off For every 4 coins, game logic adds 2 more coin
                    Off On  On  For every 5 coins, game logic adds 1 more coin
                    On  Off On**For every 3 coins, game logic adds 1 more coin

$Manufacturer's suggested settings
*To charge by game: Toggle switch 4 at PCB location P10/11 to "on."
 To charge by player: Toggle switch 4 at PCB location P10/11 ot "off."
**In operator Information Display, this option displays same as no bonus.