irc they used to make the smaller sizes using smaller wheels, i'm sure I remember reading somewhere of an audax with 26 wheels the larger frames used 700c, if i come across the pages again i'll link to them, surly did the same at one time with the trucker
found it , relevant bit below
"There are 19 different sizes of Audax frame!
These are divided into 3 different series, which are:
1. Frames for cyclists with legs too short to stand over the top tube of the smallest feasible 700C wheeled frame (500). We use 26" MTB wheels (with proper narrow road going tyres).
Sizes: 450S, 475S and 499S have short top tubes and are designed for people who are short with short legs.
Sizes: 450L, 475L and 499L have long top tubes and are designed for people who are only short in the leg"
link to full page
http://web.archive.org/web/19991014035600fw_/http://sjscycles.com/audax.htmlyour frameset was listed by the seller as Size 47cm XS 26" so that fits with the audax 26" sizes