The Altec 417 8H has 2 different production eras. Known as Series I and Series II. Series II for some reason are less desirable. It is confirmed that as Altec was going down the toilet they had Electro Voice make the last batch of Series II's. Some of them will say Made in Buchanan, Michigan. They sound great. But for the most part it's the early Series I drivers that have the most rabid following.
All 417's had Alnico V magnet assemblies. Regardless of year and production location.
Rated at a modest 100 watts. What's special about these drivers is their extended high frequency response. 60-8000 HZ.
Initially born as the 417-8 it developed into the 8H. 417-8B's and 417-8C's are just as tasty. Designed as a full range PA driver or similar application they quickly became known as an MI speaker and Altec marketed it as such. A good place to find old Altecs is in old theater PA systems that are auctioned off. A recent score for example was a sealed cabinet from the Zigfeld Theater here in NYC. I bought it at auction for peanuts and inside were JBL K120's and Altec 417 8H's.
As for the common complaint that they are too shrill, I don't agree at all. You just need to adjust your tone control on the IIC+ accordingly. It's the handling of the higher frequency that make these drivers shine.
One main problem with the 417 is the surround is very prone to decay and fatigue so unless you are getting an NOS one you might just want to get a blown Altec basket for significantly cheaper and have it professionally reconed.
For the record, Santana use of 8H's was very short. It's arguable if he even used them at all. He favored the 8C's and his original Boogies were loaded with either 8B's or 8C's.
Randy Rhodes used the 8H exclusively for a while.
Great Plains Audio in Oklahoma City is making the 417 again under their own name. Supposedly on the original tooling and manufacturing machines owned by Altec. I'd be interested if anyone has tried these.