Metal detectorists find ancient Roman silver and gold coins. So presumably if the amount of gold\silver is large enough or the sensitivity is high enough then non ferrous metals will also set them off. A brass zipper won't set them off (neither will a single bullet) but a large solid silver necklace might (as would a gun). The pulse induction technique may owe more to the ability to carry a current rather than to magnetism. They do seem to be maybe twice as sensitive to ferrous as to non ferrous though.

Sorry, but I'm no longer able to re-read it for clarification..

Someone stole the opening post! You can't trust flyertalk these days.

Presumably hijacking an aircraft with a silver or gold knife would be just as disruptive as with a steel blade...

I have a convenient small outer pocket in my backpack. One one occasion, after bag-drop, I was outside in the T5 smoking shelter (full of BA crew as usual!) and was loading this pocket with watch and wallet, cigarettes and lighter prior to Security. One of the CC commented that I was clearly a Frequent Flyer :)

They no longer use magnetrons, so it's not about magnetism. This is a myth perpetuated from decades ago when they did.
You would now need to use a ceramic blade. For good or ill, these are available and much cheaper than Au Ag alternatives.

Scanner/xray machines vary in both technology (older v newer machines) and sensitivity. Even to seemingly identical scanners at same airport but different gates having differences

I can fully undetstand why screening personel require all watches/belts removed, ie they don't want or even have time to rescreen fliers the 50% of times such metal objects would trigger an alert. Scanners are magnetic looking just for metallic iron/steel.

I do own some pricier watches i wear day2day and thus when traveling, my one personal vice. As such I am aware watches, even those with metal bracelets, such as steel+gold rolex, gold cartier do not necessarily set off the scanners.

Well don't put your full address on the outside of the bag then.

I put a slip of paper in my bags that only has my name. flight number and phone/email on it. I have no other info on the outside not even the shiny tags that show status.

On the outbound I add the name of the hotel. On the return nothing else.

I have never had the metal detector go off on my watch. It's probably too small to set it off (alligator straps with 18 ct gold parts, 18 carat gold case, but not the face, and overall rather small (under an inch in diameter). However, my hair clip with very thin stainless steel parts usually sets it off if I forget to take it off. By weight it has far less metal than my watch though.

Umbrellas and spray cans are Australian favourites. Not for stealing, but for "picking on" at security (not necessarily meant to sound critical but a folded umbrella does amuse me).

Never try to carry a spray can without the cap there if you don't want to lose it. They don't want to steal your deodorant but they won't let you take it either.. (and some would say that they want some people around them to actually steal your deodorant if they promise to use it, but that's an entirely different story).

"Spoof" them by putting the address of your workplace if you happen to work for the police? :D

I do not put my physical address on my baggage tag, and I don't even put my phone number or email address on the outside of the tag. It goes on the back of the card inserted into the tag.

Well first the OP wasn't even there. Second the OP referred to 30 minutes spent demanding to see the CCTV etc. Thirdly if you had a 30 minute saga like that and suspected malpractice wouldn't you at least report it?

And why delete the OP anyway?

If the bag went missing, I'm not convinced they would actually open it up to try and identify the owner (it doesn't seem that way from those lost suitcase stores).

I just use a business card tucked into the address tag sleeve. If the bag goes missing, they can contact my office. It protects my home and privacy, and gives the airline a place to contact where they will certainly be able to reach someone.