It looks like the Delta saw that I get to run sometimes. This saw was likely made by Delta and Dayton put their name on it. Dayton is a Grainger house brand, so Grainger likely sold it. This saw likely has a 5 or 7.5 hp 3 phase motor, since I doubt that anyone would seriously want a 5 or 7.5 hp single phase motor. If rebuilt, that saw would likely last another 40 or more years.
I get to use a Delta version of this saw sometimes, and then when I come home to my 10" Unisaw it kind of feels like I'm using a toy saw because it's so much smaller.The 10-12" diameter blades with 1" arbor holes aren't as readily available as 10" blades with 5/8" arbor holes, so finding blades for it can sometimes be a challenge. Fortunately, a machine shop can enlarge a 5/8" arbor hole to 1" very reasonably. That looks to me like a very good price for that saw, if someone has the room for a saw like this and has 3 phase power available in their shop. The one that I use has a 4'wide plywood extension table on each side that wraps around 3 sides of the saw table and it it 8' long in the out feed direction. The one that I use has an old Biesmeyer fence that is showing it's age, butit still works well. I don't recognize the fence on this Dayton saw. It could be the original fence from Delta, before the Biesmeyer and Unifences became available.
It might make a great addition to your shop.
Looks like a Dayton 3Z997. Made in Taiwan. Below is a cut from a 1990 catalog. For $400.00, that's a good start. Looks to need some work like cord, plug, starter cover, bearings, etc. The spec says it came with both5/8 and 1" arbors.