There are a number of options, the problem is your description leaves too many of those options on the table. Seperation is fairly easy to do mechanically with no moving parts, just some guides that will deflect the coins based on their diameter. Dispensing can be done with solenoids or DC motors or Stepper motors, depending on space and available power, each has advantages/disadvantages...How good are you at making mechanisms? For me it is rather easy as I have some machine tools to make parts. Are you trying to use existing hardware?