Not saying you're wrong Dfariswheel. You sound like you know exactly what you're talking about, and it was a long, long time ago. But that OP was my gun, and when I saw that first PPS in the picture above, it hit me like BANG! that the grips on that gun looked just like the factory grips used to on my OP. I've tried to find a pair like that again for my OP for years with no success.
My OP's grips were probably a little bigger than those on the PPS, but they looked just like that - which I didn't like then. The gun had been my father-in-laws. He bought it; I didn't. He just left it to me. Whe I got it I changed the grips because I thought they looked too small for a big 6" I Frame Colt. But those grips were checkered walnut, with a silver colt medallion and they looked on my gun just like those skinny grips looked on that PPS. But, like I said it was a long time ago and time does sometimes play tricks on memory, but I don't think so in this case.
Think about it. How many skinny checkered walnut factory Colt grips like that have you ever seen, even on a PPS? Not very many walnut ones I bet. But, hey, there's that one. It's got a completely different style walnut grip than what you normally see on a PPS. I know, bcause I've got both a PPS and an OP. I kept the factory grips on my PPS because they were the wider type. But I'll bet you anything that that skinny grip on the PPS in that first photo above is Colt factory original.
Now, I've seen plastic skinny grips (or maybe they were hard rubber) on PPS's before, but the PPS in that first photo looks to me like it has skinny WALNUT grips, and thats rare, and probably special order. If Colt made a non-standard grip for a PPS, why not for an OP? I'm wondering if there wasn't some particular style that had a name, that maybe you could order if you wanted to pay extra or something. That was the kind of thing my father-in-law would do. Somebody on this thread mentioned that they thought it was called a fleur de lis style or something like that and maybe that's what it was.
Anyway, I'm not trying to argue with you, I'm sure that you are principally correct and that 99.9% of OPs with walnut grips had the type of grips you showed in your photo, but then so did PPS's.....yet there's that one in the first photo above, and its got a different style of grip and I think its exactly the same style grip that was on my OP.