Garros was using deflector plates as were the Germans. However Garros had the first interupter gear fitted to his Morane. He went flying one day, shot down 3 aircraft before being forced down himself.
Unfortunately he and his aircraft were captured before he could torch it. His aircraft was then sent to Germany where Fokker got a good look at the gear and put it in his Eindeckers.
EDIT: I might be wrong

I got confused with interrupter and firing through prop solutions. Garros was the first to fire through a prop, but he didn't use synchronisation.
After doing a little reading on Raymond Saulnier (who provided Garros with his solution) it looks like the Morane may not have had the gear, only an armoured prop. Garros developed the deflector plate as an addition to the prop to avoid dangerous ricochets.
But none of it matters, us Brits didn't trust the interupter gear and held off using it for quite some time. We prefer wing mounted Lewis guns.
