Altec Mystery Diaphragms

Hoping one of the Altec experts on here can help me out.

I bought a pair of 32c horns from a local guy that came with a pair of somewhat unknown compression drivers. The drivers appear to be the 900 series bodies without back covers, but the diaphragms are a complete mystery to me. The codes on them don't match any Altec diaphragms as best as I can tell (pics attached). They both measure roughly 12 ohms on my DMM. I'm assuming that these are some sort of third-party replacements, but I'm not sure from whom. Does anyone happen to recognize them?

The horns and drivers apparently came out of an A8 VOTT system, and you can see by the pics that the drivers, aside from needing a good cleaning, have a bit of rusting and pitting on the magnets. How do folks deal with this--are these essentially on their way to becoming door stops or is there a proven way to re-freshen them? The horns are in beautiful condition, which was the main reason for the purchase, but it would be good to give these drivers a second life if they still remain decent candidates for refurb. I'm aware of Great Plains Audio, but any simple tips and tricks I can perform on my own would be greatly appreciated.
 

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ICTWoody

No longer a junior member
Those are just normal 16ohm Altec aluminum diaphragms, the measurement is about right for 16ohm. The black part on the back is the loading cap and will come off. It's probably just stuck on the rubber gasket from being installed for so long. The driver is a 902/908, ferrite magnet with the tangerine phase plug. Nice drivers.

- Woody
 
Thanks, Woody! I already own a pair of 902-8Bs which do sound very good on the 32c horns I just bought. I figured that the body was a 902/908 without the dressings, but it's great to get confirmation. The diaphragm is, indeed, stuck in the loading cap. It's the numbers on the diaphragm that are really perplexing. They don't match any original Altec part numbers on GPA's website, and a Google search only turns up a single thread out there that is basically inconclusive on their origins.

Anyone else ever stumbled upon these phragms?
 
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Wntrmute2

Not So Mediocre Member
I can't be sure but I seem to remember odd numbers on mine which I know were factory stock. They didn't match anything on the web either. I'll search for the pictures.
 
The only plus I could find is that the cheap China diaphragms don’t have numbers stamped on the back.
Maybe JE2A3 will see this.
 
I agree with ICTWoody, those appear legit, 1980s (mid-late 80s likely) OKC Altec. They are not as cool as 1950s, but I would say better than what is generally avail. today. A little rust on the driver bodies as well as oxidation in other places is pretty normal. wipe it with damp cloth--- you have done the right thing.. disassemble, and clean the gap with the sticky side of a "3M Post It" ... that is a non invasive tack with will collect magnetic fuzz hiding in the VC gap. Conventional advice says masking tap folded over... I have tried that over the years and it sucks compared to sticky "post it's" Hold it by the paper edge, and clean the gap both sides in circular motion until no more dirt. Ferrite magnets usually hold their charge just fine (as does PM / Alnico , according to the last 1940 Lansing 901 I heard, haha).
 
3M Post Its...why didn't I think of that. I initially used masking tape, but that wasn't as simple as expected it to be. I'll have the give them another pass using stickies. Thanks for the info and the tips, hifitown!
 
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