At a business, a secretary, almost always a woman, would answer the phone for all calls. There were no direct lines into anyone. If you were in she would transfer the call to your office. If you were out she would use this pad to take messages. When you came back in to the office you would always stop at the front desk and you would be handed your messages.
Why past tense? These remain far more useful than answer phones; or visual voicemail with AI transcription, or whatever. All the info you need, right there. The more I pay for digital services the more I am learning to appreciate how effective these are. Basically we are spending a fortune in development to replicate exactly these.