How old is this Claud Butler?

[SueStephenson]

My elderly neighbour is not online and has asked me to try to find out more about his old Claud Butler. He tells me it has a 23" frame and a serial number as follows:
507
4085
83

Can anyone help him to date this bike please?

 

[SueStephenson]

Re: How old is this Claud Butler? - I forgot something

... at the bottom of the serial number, there is an H. So it's
507
4085
83
H

sorry!