This lock with the keys weighs around 2.5 kg.
It has 13 levers, with anti pick serrations.
The middle lever is designed to block your pick from moving back and forth under the levers, by the way it slots into a grove halfway up the curtain.
Its has a broad centre post to block most pick tools.
Its has a curtain in the keyway too.
It is a well designed. Heavily engineered, beast of a lock.
Heres the pictures, many thanks @MartinHewitt.