Messerschmitt Bf.109E - Swiss users

In April 1939 eighty Bf.109E were bought. They were delivered from that month until just before the German invasion of France in May 1940. Those Bf.109Es were supplemented by an additional eight licenced manufactured from spare parts by Doflug at Alternhein in as late as 1944. Those were dubbed as "SuperSFR" as they had a bigger antenna and extra-cables.
When the battle of France began, the Swiss fighters began to intercept German flights intruding Swiss airspace. That way, for instance, on 10th May 1940 Many Swiss Bf.109Es intercepted a German Dornier Do.17 close to the border at Bütschwil, forcing the bomber to land near Alternheim.
Shortly later, on 1st June 12 Bf.109E were launched to intercept a force of 36 unescorted German Heinkel He.111 belonging to KG.53 that were crossing Swiss airspace to bomb the Lyon-Marseilles railway. It was then when the Swiss Air Force got its first casualty when the Bf.109E of Sub Lieutenant Rudolf Rickenbacher was shot down killing him due to the explosion of the fuel tank caused by the defensive fire of the Heinkels. Anyway, the Swiss managed to shot down six Heinkels.
In 8th June, Swiss Captain Lindecker led 15 Swiss Bf.109Es to intercept a formation of various German Heinkel He.111 escorted by the II./Zerstörergeschwader equipped with Bf.110 that previously, on that same day, had shot down an old Swiss reconnaissance aircraft, a C-35. In the aerial skirmish, five Bf.110 were shot down at the cost of a Swiss Bf.109E.
The Swiss Bf.109E received the famous red-white neutrality bands and they were still active until the end of the war and in some cases until the inmediate postwar, when they were replaced by better aircrafts.

Sources:
1. https://en.wikipedia.org/wiki/Messerschmitt_Bf_109_operational_history#Combat_service_with_Switzerland
2. Signal Squadron - Aircraft In action  44 - Messerschmitt Bf-109 in Action Pt.1
3. Salamander Books - The Complete Book of Fighters