Pal NES NTSC/Overclock found?

[CowHax]

So today I got something very interesting for you: I've recently bought a pal NES off a flea market with a switch on it, the guy didn't knew what the switch did or was since he got it from another guy

So I tried putting a pal game in with the switch down -It worked.

I've also tried putting a NTSC game in with the switch down -And it flickered like the 10nes chip but with the game showing up in one "frame", when you turn the switch up it plays perfectly.

I noticed that the NTSC game actually plays in 60Hz, while the PAL game plays at 50HZ, (maybe indicating a clock switch?) but I cannot confirm that.

Anyway does anyone know why the switch is there or have you seen this mod before?
I don't know when the mod is made and how fragile it has become, so I'm too scared to take it apart

[Ziggy]

Did the PAL NES have a different lockout chip than the NTSC NES? If so, the switch might just be turning the lockout chip on/off. You didn't mention... Do PAL games work when the switch is in any position?

[CowHax]

Pal games do only work when the switch is down.

I'm pretty sure the pal lockout chip is modded the same as the NTSC one (raising/cutting pin 4)