Well Dave no one else has said any thing so I hope you don't mind if I add my little bit of information to your thread.
I may wonder a bit but I hope its useful:
Ask your brother to look at the end grain of the plane this is usually where the maker would stamp his mark.I think your right to think its not worth a 1,000;000 But the worth is in the connection to your farther,The more expensive planes had a strike button on the forward part of the plane and failing this,as yours does the plane was often hit on the end grain on the Heel of the plane to bring the iron back before hardening the wedge down.
This act alone could destroy the makers mark. Its not always the case that the maker of the iron was also the maker of the plane and vice versa.There was a lot of sub contracting that went on in Sheffield.The W&P plane iron in the plane may well be laminated but at first this may not be to obvious but just look at the side of the iron and you may well see the snotty weld joint made by the blacksmith.
David Ward originally produced joiners tools on his own and was joined by Henry Payne in the mid 1840`s
Not to over state the quality of W&P to highly but I don't know if you have ever heard of the so called English infill planes, that where originally IMHO produced in Scotland by the firm Spiers of Ayr,Spiers very early on had plane irons fitted that where produced by Ward and Payne.
The English firm of Norris of London IMO copied the Spiers model with a new way to set the iron depth and dove tailing the cheeks to the sole of the plane a practice still carried on today by the very top individual plane makers Norris also used W&P and Sorby for there plane irons but also plane irons with there own name on,
was that just more sub contracting.
In January of this year on UK flea bay I saw a Norris A4 go for over6;000 British pounds sterling, that plane will never see another piece of wood, shame really.
Now this is foggy really but in the dark corners of my mind I seem to recall that the firm W&P was bought by a firm called Hildick,I do have a old long series paring chisel from the firm Hildick and the quality of the steel is A1,but the name of Ward & Payne was so big that they kept on producing sharp edge tools with the name on the tools.
If you consider this strange think on the British firm Record who took over the firm William Marpels and sons,and W Marpels kept on producing tools later Record Joined with the firm Ridgeway
Yet to day I doubt whether Record, Ridgeway or W Marpels make any tools what so ever and yet you can walk into any box store and buy tools labelled Marpels ,Ridgeway.
Funny old world?
Any way I hope I haven't bored any one and back to your last question,cast steel was originally produced in Sheffield by Benjamin Huntsman in 1740 almost 100 years before the firm of Ward and Payne ever existed. BIlly