Thanks for the additional detail, tooki! You are obviously much deeper into ancient and semi-ancient Macs than me. I never had any of the old Macs when they were current -- far outside of my price range, and actually too "closed" for my taste. But the packaging and user interface was so cute...
When the original Mac was launched in 1984, Apple ran a promotion in Germany where you could borrow one for free for a few days, to give it a spin. (The local Apple dealer handed you a complete system in that nice carry bag, after having taken a copy of your ID. They did not check your bank account to see whether you stood any chance to buy a Mac, so even poor students qualified for the promotion.
) That's as close as I got to one of these, back in the day...
[background]1993-2008 was when I was seriously deep in the Mac tech world. Back in the 90's, you could tell me any Mac model ever released and I could recite the specs, its quirks, etc...
From 1999-2006, I was a moderator and then admin of the forums at MacNN.com, at the time a leading Mac news site. At its peak, we had over 60K registered members, of which about 30K were active. To the best of our knowledge, the biggest Mac forum at the time until Apple's forums came along.
In 1998-99 I worked at Apple dealers, 2001-02 I worked as an onsite Mac consultant (oh, the joys of extension conflicts... back then I could tell you what every single of the around 200 extensions on a typical graphics pro system did, which ones didn't play nice together, and what order they had to load in to work properly), and 2006-08 I worked sales at Apple retail.[/background]
The closedness of the Mac was always wildly overstated by critics if you ask me. Other than being single-source for the computers themselves, the ecosystem was fairly open. There were commercial and shareware/freeware programs that tweaked damned near every aspect of the OS. Classic Mac OS wasn't locked down with code execution protection like it is now -- any extension could "trap"* (patch) the OS in any way it felt like, and it was widely done. Third-party hardware was actually quite plentiful (though if it was Mac-only, due to the small numbers it was made in, was often more expensive). The thing that made people
think that stuff didn't exist for Mac was the simple fact that you couldn't find it at mass-market retail, as you could for PC.
As for weird knowledge of the old systems, I've started to worry that a) my own knowledge is fading, and b) it somehow needs to be documented for future computer archaeologists. From SCSI voodoo, to the insanely complex rules for populating RAM in some machines, to the display adapters, to the simple reminder that ADB is not hot-pluggable, to what all the extensions did, to how fonts worked, to the neato old "
snd" resource format**, or that most 68K Macs won't boot if the backup battery is dead, or that the Mac Classic contains System 6.0.5 in ROM, with a key command to boot from it... etc etc etc.
To the chagrin of many, Apple took down its vintage support documents a few years ago. They're incompletely archived on archive.org, and some other sites have amassed a ton of it, but a lot has simply gone missing.

I think Apple did the try-before-you-buy thing in other places, too.
*People don't realize this, but on Macs until about 1997, a substantial portion of the core OS was in actual mask ROM. In the first Mac, it had 128K of RAM and 64KB of ROM, containing much of the OS, allowing things to be run directly from ROM instead of having to consume RAM. But because it's impossible to write bug-free software, the OS included a mechanism, called trapping, for the disk-loaded portion of the OS to "trap" a resource or instruction, to run a replacement version on disk instead of the one in ROM so that a buggy routine can be replaced with a fixed one. So unlike some OSes, you didn't have to rely on weird runtime code injection and the like to alter the software. The same trapping mechanism works for a system extension to trap a resource or instruction in the OS files themselves. This was widely used in the late 80s and 90s for third-party software to alter the OS in pretty much every way imaginable, from serious stuff like enhancing the memory manager, to pure fun like an extension that made the item being dragged by the mouse dangle with gravity and inertia.
**in addition to allowing PCM samples, it supported various forms of compression that were decoded in hardware, to FM sound synthesis instructions that were sorta compiled in software by the Sound Manager to run on the sound hardware, and the rendering of which varied between versions of Sound Manager. Those sounds -- like the "Simple Beep" system sound -- not only sounded different by Sound Manager version, but literally cannot be played back or converted by any known software on a modern OS. (The Simple Beep, for example, is fundamentally a sine wave, but with various filtering applied at different parts of the sound. Sound Manager 1 and 2 could only synthesize a stepped square wave approximation of a sine, which after filtering gave the Simple Beep a very distinct and IMHO pleasant sound. On Sound Manager 3, the same instructions are rendered using a true sine wave, giving it an entirely different, sharper sound.)
I always wanted an LS-120 drive, too. I haven't been able to confirm this, but I want to say that it was one of the only drives aside from the internal floppy drives on Macs that can read 800K Mac-format DD floppies.
No, they are not able to read variable-speed GCR floppies at all. Their support for regular floppies stops at MFM.
Adding to the confusion are that there were multiple models (SD-USB-M, SD-USB-M2, SD-USB-M3) labeled "For Macintosh" and yet without any 800K support. I think the changes were more to do with software compatibility.
OK, thanks. I wasn't sure about it. Too bad. AFAIK, the only way to get data off a 400K or 800K Mac floppy is with an actual Mac floppy drive.