HP 19BII battery door on back: how rare is it really?

[jebem]

I couldn't find information about the production years for this later version using a battery door on the back cover.
I understand this later design fixed the flawed design used in all the previous clamshell models and versions, where the battery door is on the side.

Considering the extravagant high prices asked for these later version, I wonder if the production batches were very limited.
I have a chance to acquire one specimen is reasonable condition for around 40 Euros and this value seems quite low when compared to what TAS sellers are asking currently (and yes, I checked the TAS sold items as well).