I have never seen a Model 10, except possibly the heavy-barrel guns, that DID have a pinned front sight. The vast majority of all fixed sight S&W revolvers of all models and calibers have front sights forged integral with the barrel.
The non-pinned sights started in 1899 on the M&P series, and even earlier on the .32 HE (1896).
I have seen several references to the pinned sights going away with the Model 10-5. I know sometimes the pin is Very hard to see and I have seem people swear their sight was not pinned - until put under a magnifier.
The pre-model 10 target models all had pinned front sights, and many other guns with adjustable sights have pinned fronts, but not a standard M & P or model 10.