There was this 1/2 inch mortise chisel on eBay that nobody seemed to love.  It sat until closing at $3.99.  Thick early socket, and you could see where the socket was welded together.  So, rather than leave it unloved, I bid.  And got it. 

In person (it just arrived minutes ago) It is all I thought it would be, and maybe a bit more.  The forge weld line where the socket was closed is clear, but tight.  The cast steel is clearly visible where it was forge welded to the iron back and socket.  I can't make out the first initial, but Ibbotson is clear.  Thomas Ibbotson was a notable maker of edged tools who started business in the first quarter of the 1800s, bought out by Marples in 1905.

New handle but true to the pattern that was surely here originally.  Read to sharpen and use.

Thomas Ibbotson was in Sheffield, so I am thinking you have a nice piece of the best hand made steel there ever was :)

NICE CHISEL & GREAT PRICE!!.

The last time I paid $4 for a mortising chisel was 1983.  I was honestly shocked to see this one with no other bids.  The one I bought in '83 was made by W. Butcher (also Sheffield), and it's dreamy.  I had it professionally sharpened, and I've had to hone it 5 times in the past 30 years.  Gets sharp, and stays sharp.  I love cast steel!  In person, you can see the 1/8 inch of steel that's forge welded to the iron stock.