Robin Day 661 Dining Chair: Can you please help?  

Hi,
I have a Robin Day 661 chair that is missing it's original upholstery and it's hardware. I was just wondering if there are any experts out there who know what screws and/or mounts were used to attach the timber back to the frame, which at present has wingnuts in place. It would be nice to get the chair looking a little more original.
I noticed that the chair has the letters CDO stencilled in large yellow letters
on the underside of the seat. I imagine this refers to a council or a business.
Many thanks for your help.
Kind regards,
Tick.