Decoding Wilbers' spring numbers

Based on one data point (a Wilbers spring set up for a 180 lb rider on a Hawk) I think this is how to decode the printing on the side of a wilbers spring:

This is what it said on the spring:

59/59-280-130

Knowing that the hawk is likely to take a big heavy spring for a 180 lb rider (they're likely to specify a 1,200 - 1,500 lb/in spring), and that the compressed length is about 4-3/4", and the ID is somewhere between 2.25" and 2.5"...

The 59/59 is the ID of the spring, in mm, at each end
the 280 is the spring rate in newtons/mm
the 130 is the free length.

So our spring above would be a 1,550lb/in spring that's got a 2-1/3" ID at both ends, and has a free length of 5"

Keep in mind that this is based on one spring, some guesses, and some sloppy measuring, but it all makes sense.