Dateline, February 18, 2017:
I try not to harp on quality issues as long as a replacement part is at least functional. But this one finally failed I believe as a result of low quality issues ultimately making it dysfunctional and hazardous. I installed this one in 2007, and it failed in 2017. Life expectancy is not the issue (yet), but along the way it more than once failed to connect leaving no lights, it would regularly have headlights on when in the parking lights only position (depending on how you jiggled the knob), will shear the wires when tightening the connector screws, and finally shorted to ground burning the power supply wire. Immediately below are pictures of the failed parts after the short to ground.

The power input terminal was touching the steel keying plate when the switch was pushed fully in to the OFF position. Must be the brass contacts are a bit too long. Or maybe the plastic barrel insulator broke to allow the power terminal to touch the steel shaft. The new switch is same model as the old one. First operation had the parking lights either on or off depending on a jiggle of the knob. At least it is not shorting to ground, but it can still cut the connector wires in the harness. If it does that, then the input power wire could short to ground against something on the dash panel. Going to have to keep an eye on this one for a while.

Moss Motors has been notified again. In spite of ten years of notices and bulletin board complaints about the quality of this part, it appears that Moss had done nothing to improve it.

See more information on additional quality and non-originality issues
in the Electrical section ar5ghcle E-117

Addendum January 1, 2023:
Another Moss Motors Classic Gold MGA lighting switch bit the dirt today. They must be very proud of their merchandise to keep putting the same fancy label on the same classic junk for 15 years now. I have been buying these two at a time to have spares, since they have proven to be so unreliable. The last failure shorted to ground and nearly burned up the wiring harness. This one just gradually lost the headlight connection while parking lights still worked. Had to fiddle with the switch each time it was turned on to be sure it would actually light up. Sometimes hit a bump and headlights would go out. Finally they just refused to make any connection at all, having to change the switch again.

Being a riveted assembly requires breaking the Bakelite shell for disassembly for internal inspection. The one clean contact was the S1 terminal, only carrying 3 amps total for all parking lights and dash lights (and maplight). The half burned and half blue contact was S2 terminal for the headlight output, carrying 10 amps regularly for the two hallogen lamps. The totally burned and black contact was the A1 input terminal carrying current for parking lights and headlights together. My best guess here after failure, is that the contacts do not have enough spring force to make reliable electrical connections.

Addendum February 23, 2024:
It just happened again. Another Moss Classic Gold lighting switch shorted to ground and nearly burned up my wiring harness. This one failed after only 13 months, still under warrantee this time, but that doesn't mean I want a replacement part. Even if it was free, I won't put another one of these in my car, not ever again. In a few days I will see if I can disassemble it to get some more pictures of the failure mode.

Addendum February 27, 2024:
Dissecting the failed lighting switch. Drill out the rivets to remove the terminal posts, and the inside contact blades come along with. Then drill off the peened/swaged over tail end of the center shaft (was a hex nut here on OEM switches), to remove the internal parts, and pull the shaft out the front. The small set screw and spring and ball on the side are the 3-position snap detent. The cylindrical plastic part with brass wrapped around it provides the moving contact surface. Notice the flat silver part that looks like a flat washer with a finger sticking out one side. This is the guiding key that rides in the slot on one side of the housing to control the pull-turn-pull mechanical function of the three-position switch.

The obvious problem here is the power input contact finger is perhaps a bit too long, so it can touch the steel keying finger. This keying part is grounded through the shaft and the front threaded mounting bushing and panel nut (when the dash panel itself is grounded to the chassis. Switch off, and touch the keying finger to the tip of the power input contact, and the input power wire is shorted to chassis ground. The browN/blUe 14-gauge power input wire for ignition and lighting switches is unfused, and will carry enough current to cook the switch to "well done" at the same time as it over heats the power wire.

If you're lucky, it may burn the tip end off of the input contact finger to break the circuit like a fuse (like the one at top of page). Or it may burn off the power wire at the lighting switch terminal, or at the ignition switch (which is used as a terminal block for these power wires). Not so lucky, it could melt down any or all of the brown wires from the lighting switch back to the control box, and back to the battery power cable on the starter switch. That would be expensive to repair or replace the burned wiring harness (if it doesn't start a fire).