This is slightly OT, but I'm sure someone may be able to offer some information. I have just acquired a Whitworth tap and die set, that is a tap & die set manufactured by J.Whitworth & Co Manchester. I have been able to find out a little about Joseph Whitworth from the internet, but surprisingly little considering what an important engineer he was. One thing I did find is that after his death, in 1887, his factories were sold to Armstrong, and became known as Armstrong Whitworth. Does this mean that the set I have dates from before the time Armstrong bought the factories, or would they have continued to use the J.Whitworth brand after that time.
Regards
Kevin
PS For those interested the die is quite unusual. It is made up of 3 die sections (like Coventry die head dies) which are held in a sort of three jaw chuck arrangement which can be tightened by a screw on the side of the die stock.