also: ナンバーディスプレイ
number display
General term for a display that shows numbers, such as on a device or screen.
The number display on this machine is broken.
caller ID
Specifically the telephone service that shows the caller's phone number; often used in the context of landline or mobile services in Japan.
An unregistered number appeared on the caller ID.
From English 'number display'. The variant spellings reflect different transliteration conventions for the final vowel.