But what can it actually do?

Okay, just showed the video to the mister who has been working with computers since the '70s. He said it can do programs that have to do with numbers, like accounting or billing or stuff like that. I asked if it could be programmed to break numerical codes and he said yes. He also remembers working with punch tape, said it was a pain in the ass. Punch cards came after the tape.

Not exactly. Punch cards were already used on mainframes when mini-computers were created to use paper tape.

I thought it (turns out it was originally called the Harwell Dekatron) was perhaps part of the WWII Bletchley Park GCHQ infrastructure, but it turns out it wasn't built til 1951 . MOAR info. Not so much on the codebreaking.