Datron 4808 with an indentity crisis

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Hi team.
I have an odd question that I am hoping some of you might be able to shed some light on.  I recently acquired a used Datron calibrator from the online gambling centre (beginning with e), which I believe is a 4808, but on closer inspection, it is showing limitations in accordance with the performance of a 4805.  For instance, it can only generate ACV up to 100 kHz, and the display resolution is 6.5d / 5.5d rather than 7.5d / 6.5d.  I have lifted the lid and checked the P/Ns of all boards and all boards are matching the 4808 parts rather than 4805, so I think the guts belong to 4808.
Does anyone have any clues?  My first guess was that one of the boards must have failed and was replaced with a 4805, but even the board that houses the EEPROM appears to be from a 4808...
Thanks, Liam