At the weekend I scarfed up an unusual wooden ruler.

It's around 3" wide, and 27" long, and is made
from something like beech (at least it's a light coloured
hardwood, with a fine grain, that isn't box).

It's rather worn.

I bought it because it's some kind of scaling ruler;
it has multiple scales on both faces, with stranges labels.

I will list each "label" and the measured ratio of indicated inches
to actual inches

B18 3/4     1.0
B19 1/2      .96
B20 1/2      .9231
B21          .888
B21 3/4      .8627
B22 1/2      .834
B23 1/4      .808
B24          .7843
B24 3/4      .7582

Those scaling are FAR too big for this to be a pattern makers
shrink rule, and anyway all the shrink rules I've seen are metal.

But the scales aren't extreme enough to be an architects or map makers
scale.

And I don't know any other users of "scaling" rulers...

So what is it?

    BugBear
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