How can I tell the difference between Apple 30" Cinema Display models

According to the specs provided for the Apple 30" Cinema Display at http://www.everymac.com/monitors/apple/studiocinema/specs/apple_cinema_display30.html, Apple increased the Brightness from 270 to 400cd/m2 and Contrast Ratio from 400:1 to 700:1 in March, 2006.

How can you determin the difference between the prior and later models? Does anyone know if there was a model number change, what the model numbers are, and where the model numbers are located on these unit, or if there is some other way of making this determination?

Hopefully, Apple did not retain the same model number on both units!

Thanks,
Dennis

G5 Dual 1.8ghz Mac OS X (10.3.9)

G5 Dual 1.8ghz Mac OS X (10.3.9)

G5 Dual 1.8ghz Mac OS X (10.3.9)