When the TouchTone telephone was first introduced, it had only ten buttons, these being
the numbers only. Shortly afterwards the 12-button dial was developed, adding the # and *.
This Ericofon is the 10-button version and I suspect it might be a prototype. All the reference information I have found on the TouchTone refers to the 12-button only. No mention is ever made of the 10-button.
I suspect that by the time they developed the TouchTone Ericofon, the 12-buttons were starting to come out, so the 10-button was dropped before production in favor of the 12-button.
This, of course is all conjecture on my part.