Any model 25 that has the three letter, four number serial system will have correct thoats. If it is an N prefix, it might. As already mentioned, take a .452 bulllet (preferrably jacketed) and drop it into the chamber from the rear. Lead bullets will stick in the throats much more readily than jacketed due to their lube, so they can give a false impression. It should hang up as already described.

S&W fixed thoat diameter at about the same time that they dropped the pinned barrels, so to me, ny non-pinned model 25 is more desirable than a pinned one. I know lots of guys have posted here that their pinned guns shoot tiny groups, but they don't mention what range or size groups they get. It's just common sense that any variable that causes a problem for the bullet upon entry of the forcing cone/barrel will hurt accuracy.

An oversized throat will affect jacketed and lead bullets alike. The bullet passes through the throat tilted and engages the barrel forcing cone off center, which ruins accuracy at the worst, and doesn't do any good at the best. Using bullets that match throats size regardless of bore diameter (unless the thoats are too small, which is an easy fix) will almost always produce the best accuracy.