Thanks for the tip on the string locks and the explanation on the covers, Coachrick. It makes perfect sense.
During all the years of dropping off unwanted stuff at the back door of that particular Goodwill, I never thought of actually stepping through its front door to have a look until last year, because I had assumed that everything inside will be just as useless as the stuff I had dropped off. It so happened that this PS 125 was sitting right there on the sporting goods shelf on that particular day...
Naturally, I was instantly hooked. I couldn't believe that anyone would buy a racquet like this, keep it for more than two decades, and just toss it out like that. One man's junk may be another man's treasure, but still, people who buy high-end racquets would presumably never think of them as junk!
A few months later, I found that "Kennex" racquet at the same store; the subsequent search for its origin led me here, and eventually to this thread, and I came to realize just how much I had been missing out on by stupidly overlooking this inexhaustible supply of cheap fixes for racquetholics. One immediate effect of this late realization is that I am now completely weaned off of Play-It-Again-Sports.
After the initial find, I made the rounds of every thrift store within a 20 mile radius of my place for a whole week to see if this was a common occurrence. unfortunately (or perhaps fortunately, for my wallet and sanity), it wasn't. And clearly, not all thrift stores are created equal. The ones bordering the more affluent neighborhoods are definitely better stocked. I am told by the staff at "my" GW that during much of the year, they tend to sell what they collect locally, it's only during the peak donation seasons (spring cleaning, Christmas New-Year) that they would pool everything at their main distribution center so as to spread the goodies around. This greatly reduced my urge to explore beyond my immediate horizons, and made it easier to rationalize the high frequency of store visits to myself.
Below is the rest of my haul over the last 10 months. As you can see, nothing spectacular there (although I rather enjoy the Spalding Smasher, which was unknown to me). I guess I have averaged a little more than one pick-up per month. A good bit more than the 2-3 per year rate I was keeping via PIAS, but for about the same price. I will probably have to be more selective in the future to make this a sustainable habit however.