D'Alton is a very good maker. He obviously specializes in those multi segment handles.
His grinding is excellent, and he nearly always mirror polishes... and if you don't get the hollow grinds smooth, mirror polishing shows all the flaws. I.e., you gotta be good to have the courage to mirror polish...and D'Alton is good.
D'Alton nearly always uses ATS-34, and if not it's damascus.
I talked w/ D'Alton at the 2000 Guild Show. So as of that time stamp, he was sending his blades out to a professional heat treat firm near his home somewhere around Phoenix.
I forgot the name of the firm, but it's owned by the guy who owns Ping Golf Clubs, Karsten. So it may be called Karsten. Karsten doesn't just heat treat clubs, he does other stuff, like heat treat work for machine shops if I recall what D'Alton told me. He said they use big industrial vacuum furnaces, and the knives come back with zero scale and no warpage, so he is pleased with this service, as it shortens his final prep time. That implies that you should get a very reliable heat treat out of D'Alton, and that his ATS-34 should perform like it should at Rc59 or 60 or whatever he specifies. I.e., they ain't just purty, they would actually perform well I suspect if anyone had the courage to use one.
D'Alton actually handles heat treating for other makers... he accumulates batches of blades (I assume ATS-34 and 154CM) and then sends the batches through Karsten to keep the price down. Often times heat treaters have a price they charge for the whole oven to run through a cycle... and you can have 1 blade or 100 blades in that oven for the same price.
Golf clubs are heat treated, so that may be the genesis of why this big heat treat business came to be.
From Ping:
The heat treating of clubs was also pioneered by PING. After casting, the clubheads are heat-treated in a vacuum furnace to stabilize the metal and give it the necessary corrosion resistance and durability. Importantly, heat-treating allows clubheads to be adjusted for loft and lie for years after purchase.
Here is D'Alton's web page:
http://www.dholder.com/pages/bio.htm
I own one of D'Alton's "My Knife" patterns, and it's a real beauty... stabilized dyed spalted maple, cocobolo, and red amber. Sorry, don't have a pic to show off. It's not one that I use... a bit too pretty.
It looks a lot like the top knife in this pic from D'Alton's page but has deep red amber spacers:
http://www.dholder.com/images/my_knife.jpg
D'Alton's work is first rate and his wife's (Pat) engraving is excellent also.
There is one thing you should know about multi segment handles like this. You can see D'Alton uses red (felt?) and metal spacers between segments...makes for a really unique and beautiful handle (that's probably as much or more work than the blade). Every one of those elements in that handle has a different propensity to swell and shrink with changes in temperature and humidity. So you can't expect that handle to be perfectly smooth forever... you can feel the seams. I suspect it leaves his shop perfectly smooth, but over a couple months, you start to feel the joints... by probably less than a thousandth of an inch or so (which is easy to feel with your finger). You might be able to mitigate that somewhat by waxing the handle. Don't let that deter your purchase of what I think is a really classic, high quality, beautiful multi-segment-handled hunting knife by D'Alton Holder. Just a heads-up. This styled of handle is really his trademark... and he does it as well or better than anyone.
P.S. D'Alton is a super nice guy also. A real gem of a guy to talk with ... things weren't too busy at Guild, and he spend probably 15 minutes with me talking handle materials and grinders, etc.