crowns are 26.4 and 27mm. if french, usually it's 26.5mm. they're close, but are off just enough to require heavy drinking. i recently had my moto gr crown milled down to the 26.4 standard to fit an english campy headset that i paired with the two threaded pieces from a french set. i couldn't find a complete french campy sr headset for less than a million dollars, so had to join a couple orphan sets together. concerning stack height, the set came up a little short for the old frenchie, begging me for either a dirt cheap 1mm notched washer that's an appropriate silver color, or to replace the rust colored, flat-sided, 2 pound washer original to the moto. i went with the pretty, cheap and light notched one that isn't made for flat sided french steerers. but after reading this thread, i'm now scared i ruined the threads and will be forced to dump the whole bike in the puget sound and officially commit myself over to the local buddhists.

so ... right after i did all this i found a complete headset on craigslist that would've saved me $30 and a lot of hassle. this kind of thing happens, and it's important to have past hobbies, such as guitars, that one can run to for solace and then pawn so as to continue the vintage tinkering.