Go Darley!
As most of you know (and some have operated), My truck is W.S. Darley equipped. Darley took a '65 GMC 4000 Cab & Chassis and added a (very) plain tanker body and a front-mounted Champion 500 gpm pump.
My pump is kinda interesting (well, to me, anyway) as it was built late in WWII on the war contract, but never delivered -- it didn't leave the Darley factory in Chicago until 1952. And on the front of a '52 Ford F-600 truck built for the Quincy, ILL VFD. Quincy turned that truck in about 1962 or '63, and Darley rebuilt the pump and sold it again to Seymour, ILL VFD on the front of the truck I now own. I guess the Seymour Elementary school students didn't cough up much of their lunch money as my truck is probably the plainest, least flashy fire truck on the planet. Amish communities have fancier rigs than this

It hadn't seen much use, either, as it had less than 8,000 miles on it when I bought it.
Darley is still family owned and operated (into their 2nd century). When I called, looking for a manual for my pump, I spoke to a member of the family who then pulled the file on my pump, photocopied everything in the file and sent it to me (along with the manual and a Darley hat). That's why I have the history on my pump.
From what I've seen, I guess Darley's are rare here on the East Coast? 51Ashton's is the only other one I've seen.
Regards,
John