It's impossible to tell because the different part is on the inside. It could have been reconed, virtually all recone kits available post series 2 days ended up being the pro line kits.
If you have the factory original parts, the driver would be labeled "pro line" somewhere in the model number OR another way to tell is that it would have the EV factory part numbers as follows (8 ohm)
EVM-15L series 2: 815-0180, 0529, 2012, 9462
EVM-15L Proline: 815-2057, 2072 and there may be others but my factory service data ends 6/1/1992