According to bhtooefr on
this thread, these were early buckling spring boards. Anyone use them or have any information on them? Info is rather scarce on the internet about them. I've been able to get model numbers (1742700 for a model like the above, 1742705 for a model with 12 addition F-keys to the right of the keyboard) but that's pretty much it.
Some pics of it
here. Note the G with the serial/model number. Bit of a wild guess, but maybe was this the Model G? (bare in mind that the letter assignment was not sequential, for example, the Model C came
after the Model F.)