Not sure what to do now. I might leave using it atm until I research a bit more . There are some overseas auction houses [ I am in Australia and there is not too much here] that specialise in engineering tools etc who may be able to help with age etc. It is currently in a velvet lined wooden fitted case with the outer covering a bit battered but otherwise good condition. Will report back when I know more. I agree with Marv about what it is, but it gives me a starting point for further enquiries . It may be a bit too old and rare to muck around with too much.
Regards, Peter.