The 'tube-transistor' enigma by MC carts?

Raul indicates "bobbin" is synonymous with "armature", just different terms for the "thing" they wind the coil-wire around. Is "core" another synonym?
I ask because there is also the "air core" design, where the coil-wire is wound around — nothing. Thus there is no interaction between the different materials, hysteresis, or "magnetization" of an iron core.
As it was explained to me, the "air core" is wound around something of course, it must be. They use — Ice. The wire is wound around a sliver of ice of the right shape, which then melts away, leaving no core/bobbin/armature at all. Hence "air core". This must be done in a deep-freezer, of the walk-in kind.Fidelity Research used this method in some of their models, as it was explained to me by a FR aficionado I knew many years ago. Maybe he was wrong, maybe nuts — but my FR MC-201 advertises its air-core as a feature that offers lighter moving mass and lack of the interactions mentioned above.
Do any of you know more about this?
I’d like to think he wasn’t crazy. I bought several FR cartridges from him, because of their sound of course, not the ice-theory.

@chakster — Thanks, I think I have that text in the booklet that came with it. But a question...

" Air core coil is adopted as coil.... In addition, by adopting a new special lightweight resin coil bobbin...

It seems "core" and "bobbin" are different things. I thought both referred refer to whatever the wire is wound around, i.e. a single thing — apparently not. So now I don’t know what an "air" core is. Can someone educate me, and explain the difference between core, bobbin, armature?

@lewm — More resistance would lower the output, yes? But we’re dealing with low output anyway. Would it have any other significant effects?

it’s nice to run into somebody with an FRMC201. I have had one for a while when I picked it up on a curiosity. I absolutely love it.

Likewise, Analogluvr. I got my first 201 at an "Audio Swap Meet" near Los Angeles in the mid-90s. I knew nothing about it and only went out of curiosity and proximity. Turned out to be a famous event, not just to buy or sell, but to network with audiophiles worldwide. I met dealers from Japan, Korea, Russia, UK, Germany, Italy etc. They not only paid airfares and hotels to be there, but shipped lots of amazing gear halfway round the world. for a one-day event. Everywhere I looked there was something I wanted. Then Ebay arrived, and the swap meets ended. End of an era — when ’progress’ means an end to all human contact, I question the word...

That 201 was used but quite good condition. and sold for next to nothing. A year later I got one NOS NIB at an even lower price, one of those rare unbelievable scores. I still have it, unused, for future use. It’s not the ’greatest’ MC by any means, but has a wonderfully holistic way with music; a Fidelity Research hallmark I believe, judging from other FR models I’ve had.

@nandric — A poem? From a mutli-leveled literary stylist like you, that’s high praise!
@analogluvr — One brief vignette how cool that meet was. I approached a table laden with goodies. I saw a clear plastic bag stuffed with, bursting with, cartridge-mounting nuts, bolts, washers, gold cartridge clips, 1000s of them, for $3. My hand was an inch away from it when my eye caught something less than a foot away — still-sealed new Shure V15 IV-MR for $40. "You're Next!" I thought as I turned back to the $3 bag – but someone was buying it. Too late! I reached for the Shure and someone was buying it too. Damn! "But I saw it first!" didn’t work there, I didn’t bother trying. Two great things lost in half a second. Never again! I moved to the next table ready to pounce...