Hi!
It's very hard to say. I had to check in my Leatherman add-on (the little hold for the hex bits and a few bits) while a lady next to me was carrying her extendable (pretty pointy) hiking sticks.
There is a quite general rule that leaves much space for interpretation in the IATA Dangerous Goods Regulations (DGR). My experience is as follows: the more common the item, the better the chance to take it with you.
There's also a section on diving equipment (flash, torches, tanks, oxygen, ...). The only problem is that the DGR is hard to get (they cash for the copy).
IATA website
Some check-in personnel doesn't really know it and it depends on the mass of divers they've experienced. I had severe problems to take my torches on board as carry-on in México City e.g..
I had to late-check-in the torch which resulted in some problems to get it at home (it didn't show up on the belt but was kept at the lost-and-found). That's an option.
What I now do (it's the hard way and you possibly fail) is to ask for a written statement by the airline. That may include to send them some specification (photo, dimensions, info on the material) if they don't know what's it all about.
I stuff all the bits that will survive check-in into my trunk, the more sensitive parts (torches, housing, camera) are carry-on.
Cross your fiongers, I'm leaving to Cyprus tomorrow. 20K allowance. There will be lots of discussion about the devices I'll carry in my pockets ;-)
Helge ;-)=)