First, they can not be in serial mode. (No MDB or NRI communication protocol.)

Then it's not difficult - there should be one wire for output on each coin accepted. These are wired to the coin switch wires in the game. Connect common and +12v, and you should be good.

Relays come into effect when you want to accept more coins than the game has coin switches. (I. e. 4 coins, but the game only has three switches.)

Switch Matrix?
Ah, sorry, I missed 'early' SS. (If you have a specific game, it does help to link to the game.. )

In this case, if the coin mech has a switch common seperate from the voltage common (some do, some don't), then you want to connect the column wire to this, with a diode as in the switch matrix. Then each chute wire to the coin outputs.

If the mech does not have a seperate switch common, then you will need to use some small relays, with the switch matrix wires going to the relays (with diodes as specified in the switch matrix) and then the relays Coils connected to the mech outputs. (Use small relays - Check max current output of coin outputs on mech! Or you will fry the mech.)

'Switch Common'? If it is on the matrix (I mean, a row or column, which require diodes) then no, do NOT wire or join it with any other wire. It shook D ONLY go to the mech switch common. If the mech does not have a switch common, then relays are needed.

If the 'switch common' is ground, then it can go to the switch common connection if they're is one. Otherwise don't connect it at all.