We are used to having hundreds of megabits or more per second of data transfer rates at our fingertips, over the Internet, straight to our desks. For higher-end connections, even multiples of gigabits per second isn't at all uncommon. This makes transferring even large amounts of data basically trivial. Large storage media is also common, allowing us to store the data both prior to and after transfer.
However, that's a pretty recent development. It wasn't more than some 30 years ago that a 10 megabit per second connection could be considered a fast local area network, and a few hundred kilobits per second was a respectable inter-network link. Only some 15 years ago, a hard disk on the order of 100 GB was on the large end of the range.
In such an environment where what we might today consider high-speed data transfer simply wasn't a thing, how was radio telescope observation data transferred between science teams, and between locations?