The labelling of the t5000 series has changed over the years and some examples are shown below. When you look at them you can see why the older models are often advertised as a "t5000" (very helpful!) and newer models as an "HSTNC-...".
This is label from the first thin client I got hold of - it is also the one with earliest manufacturing date. It identifies itself as a t5000 1G with a part number of 336448-001. HP must have subsequently revamped their numbering scheme as this hardware is identical to the t5700. (See next label).
About a year later we have the t5700. The details on the labels have now changed. We now have:
Model : hp compaq t5000
SUBASSY : t5700
Product : DC639A
With the t5530 (3 years on from the above) we have:
SUBASSY : t5530
Product : 436673-001
With the t5730 (1 year on from the above) we have:
SUBASSY : t5730
Product : 463335-001
Any comments? email me. Last update December 2011