Looking for information about these chairs

I have 4 of these chairs, they belonged to my father and have been in my family for as long as I remember. They were in the house while I was growing up in tthe 50's and they were old then. My father, who was an excellent cabinet maker and worked in the original Ercol factory in High Wycombe, always said they were 'good quality' chairs. If any one can shed any light on these chairs, what type they are or how old they are, or any information at all really, I would love to hear from you. Thanks