How can you tell if the fenders on your T are original or repops? Is there a thickness difference? My 1910 has extremely good fenders/running boards and splash shields; in fact they appear almost too nice for 107 year old metal even if they were perhaps blasted and painted years ago. Is there a way to distinguish between originals and reproduction?

Bill,

This wont help you, but I knows um' when I sees um'. Past that, I can't offer much more advice. Later fenders are pretty easy to tell. Mostly, older fenders that are repops just look way too good. Almost every original fender has a "tell", usually on the underside.

I agree. The fenders on my recently acquired 09 are in better shape than on the 1924 coupe. They look almost as good as the repro fenders on the town car, which I bought in the early 1990's. The ones that confuse me are those on the 14 Touring. They look original with just a little tell.
Even so, we believe the 09 was restored in the early sixties and the look really good.
I really think that manufacturers of repro equipment would discretely add their name, just like Texas T did with their repro whistle.

OK this is probably a dumb question, but whats a "tell"?

Tell = Clue.
You can usually tell by the rivets and the edge rolls. Fenders that didn't come with the mounts may have bolts or "down-home" riveting.

I once bought a T which had repop front fenders on it. Under the hood shelves, they were stamped (impressed) with "1917-25 Ford" or something like that. The car was refurbished in the 1950's.

Sorry Bill. Not a dumb question. As Stephen states, it's a clue. Most often used by card sharks to "tell" if a player has a good hand. Like if a player's eye twitches every time they're about to lay down a good hand.