Mohtaram fadedjeans Sahib,
You get what you pay for. I suppose yours was a Tri-Circle lock which I gather from you saying 'grey' as its colour. Please select a steel lock, Unity one or preferably go for Abloy which is a global leader in security offered by locks. Check out this link and get one which fits your Mehran: ABLOY Padlocks. If you go for Abloy, your car cannot be stolen. If you can't find an Abloy, then go for any Chinese one available in Pakistan by the name of Unity Locks.
The Tri-Circle locks available in the market today are substandard knock-offs (copy) of the original Chinese 'Tri-Circle' brand and are being manufactured illegally in Sialkot. If you buy such substandard quality to protect your car then one day hell will break lose and you will end up losing your car. Get a good Chinese steel lock, Unity is a good brand and if you want the ultimate, as I've mentioned in my previous posts in this thread of mine, then go for Abloy. I've mentioned about the Abloy brand in quite detail in my post number 46 on page 3, click here to go on the page and look for my post number 46: https://www.pakwheels.com/forums/news-articles-driver-education-safety/219208-how-protect-your-corolla-theft-3. Abloy is a hell of a lock and you won't have any sleepless night if you put one in your car, believe me!
Tri-Circle can be easily picked or cut by an experienced car thief, small wonder that you have told us that the grey chips of this substandard lock were found on the floor of your car, for both its shackle and body can be easily cut with a proper tool.
Regards.
