Seems like an excellent time to point out that 2 1/2 inches is actually 63,5 mm. And that 65 mm is 2,559 inches, that 2 9/16 inches is 2,563 inches (who wants to quibble with 0,004 inches?), that 2 5/8 inches is 2,625 inches, which is 66,68 mm (can we approximate this to 67 mm?).

Also seems like a good time to ask ---"Are there really any 2 1/2 chambers on those old double so marked?"

But, what is 1/16 of inch among fellow posters, especially in the midst of a lively discussion? Even 1/8 inches?

Niklas