Looks like the horn has been stored on its side at some point.
Is it the right shape otherwise?
Is it usual to find this machine with a two spring sound box? I've only seen these with four spring sound boxes, and the smaller/earlier models with two spring ones, but I haven't seen that many
If you are interested in this machine, I would recommend that you go see it, or as a minimum, request several photos of everything exterior and interior - otherwise you risk to be very disappointed, 4,500 GBP worth of disappointment. An electrical machine is especially tricky, photos will not help you much, you would have to assume that the motor will need to be rewired, in its original condition it is probably a fire hazard. The horn looks ok from the photos, no way to tell if its bell is still circular or is oval, and these machines did not follow rules as to what type of soundbox was sold with which type of machine. They were highly customized and made with high degree of variability in motors, soundboxes, and even cabinets. Expert even offered to make conversions of other brand cabinets. Two- or four-spring soundboxes would be equally offered irrespective of the machine. I have an Expert Junior with a four-spring soundbox. This one looks like an Expert Senior.
Have you noticed that there is no picture of the right hand side of the case?
Could it be that the power cable enters it through a redundant winding hole?
The patchy availability of mains electricity in the UK prior to the creation of the National Grid resulted in machines being converted from spring to electric power, and vice-versa, when the owners moved house. If this machine is a conversion it should be declared as such and reflected in the asking price.
I would not even think about spending this sort of money on any machine unless I had seen and heard it in person.