HP 71b: Oregon Digital Environmental Case

[Michael Fehlhammer]

Meanwhile the case arrived, and there are evenmore questions.
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I will have to replace the old corroded batteries. At first sight I had no idea how these batteries were charged, because there is only one connector (D SUB 15 pin, male, game port type ).
That connector seems to be a all-in-one-solution, what can be seen from the two plugs that came with the device:
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The left one is for establishing a serial data link, the right one seems to provide a connector for an AC/DC adapter. I have to find out the polarity. Since there are five cells, giving 6V, would a 8V charger be the best choice?
Interestingly the HP IL signals are ducted outside the case also.
The seller told me that the case was used for surveying tasks; it had been connected to an instrument called Regelta (Carl Zeiss), a tachymeter. Maybe this case was custom-built by Oregon Digital?

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What could be the task of that add-on board connected by a ribbon cable?
These two oval objects coated in kind of black shrinking hose, connected by a black and red wire - are additional batteries? Sorry for stupid questions, I don't understand much about electronics.

I really would appreciate any comments, tips and help.
Maybe somebody knows someone who knows an engineer who worked for Oregon Digital? :-)
For example the pin asignment of the connector is of great interest ( in order to use the serial interface - provided that it is compatible with HP 82164a, if not - well, I would need the MANUAL! ).