It has been suggested an old school LCD/LED clock could have been there as they were options back in the 70's at one point but I have not been able to find any examples of such items.
In 1974 LCDs were still in the lab widget stage and the only LED wrist watch on the market was a Pulsar that gave you time or date and cost $425. Put my Bulova Accutron in the drawer to buy one. The technology would have been a little steep for a car accessory.
The holes could be a byproduct of the panic button craze. I had mine screwed to the dash of my '74 Charger. Whatever went in those holes wasn't factory or dealer installed.