I do know the difference. The Ra 162 has a maximum sheet size of 44.09" front to back and the Ra 162a has a maximum sheet size of 47.24". Plates and blankets are different in order to accomplish this. Other than this size difference, the machines are the same.
Are you looking to purchase a machine?
Feel free to contact me directly at 563-249-3252 and I can answer any other questions you may have.