it's, according to the documentation for a 2300, a 7 speed hyperglide 13-21 freehub. described under a misleading column titled (FREEWHEEL/CHAIN) as: "(fw) Shimano 13-21, 7-speed (c) Shimano Hyperglide". i guess they were still referring to it as a freewheel at that time.
in another column titled "HUBSET", it states: "Shimano Ultegra sealed 32 hole w/QR".
please feel free to verify. the doc link in post
#37 is a PDF. there is a grid with all the components for all the models on page 4. you'll have to blow it up about 400% to read it though. of course, you could just take my word for it.
