Thankyou Arc Tourist - and for your photo's - I can now see the correct arrangement for the pinch bolt which has been crudely adapted on mine.That's a Swinden's. Nice find, and worth a fair chunk of money.
I acquired one awhile back, refurbished it and find it to be a more practical and useful vice than others I have.
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As Dcal advises - they still make them and in view of its possible value it may will be worth investing money in to restore to original condition.
I will post some pictures of the progress in the days following.