Yes, the earliest have two spark suppressors which are noticeable underneath. On the very earliest the strobe light wasn’t on all the time, you pressed down on the speed trim dial to turn it on, both these versions having flush strobes, and also the next version with one spark suppressor built in to the power switch. The ones after this had raised strobes.
Don’t think firm dates are available as the records were destroyed in a fire.
“Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”
Hunter S Thompson