The difference, I think, between the Optimus 8 and the 8R is the automatic cleaning system of the R. Inside the burner is a tiny gear driven brass block, with a needle attached. As you rotate the burner to "on" it goes first to full on and at the end, the cleaning needle pokes up through the gas jet to clean it. It doen't completely kill the flame (usually) and you can rotate the knob back to full on and keep on going.
The earlier ones have no brass block/needle. Instead, they came with a separate pricker that you would use to manually clean the gas jet. Don't know if that answers, but that's how mine works. That little brass block with the needle is available if yours is broken or lost.
If you want to learn more about brass stoves then you ever knew there was to learn, go here:
Classic Camp Stoves
While I can appreciate the cool factor of "brassie's" they actually don't work all that well, except for boiling water. For the most part, they have binary operation-off, or fully on and roaring. They are very simple dvices and so might make good end of the world stoves as there are 3 moving parts.
I always wanted one of these because it looks cool:
Optimus 22 | Classic Camp Stoves
And lastly: RustyTLC-I'll trade you my best Optimus 8R for a Coleman Solus. JLMK.