What the hxxk is this Speaker Out connection of Vintage Solid State Amp?

Hello,

I recently got very old (60's) vintage integrated amplifier and it has weird connectors throughout. All of Inputs are 5 Pin Din which I understand.

The Power Cable Input has 3 Pin Din which I may be able to find a suitable connector to make one power cable.

However, the speaker out connector is weird and I have never seen one like these. Does anyone enlighten me what this connector is called and how I can connect to speakers?

Thank you...

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