Hey guys, here's a math problem that's just a little beyond my comfort level.

Question is: for what size wheel/tire is this mileage meter correctly calibrated?

Here's the story: I rescued this old mileage meter from the trash at the bike coop last week and installed it on my '58 Raleigh. Before our ride on Saturday, it read 370.9 (photo below) and after the ride it read 395.5 (photo below).

Between the two photos, we rode 38.29 kms / 23.8 miles according to Bike Route Toaster.

My bike has 27 x 1 1/4 tires on it.

So... would this be accurate if my tires were 27 x 1 1/8? Or 700 x 32c? Or what?