That's interesting, especially if it has info on ways of identifying steels where micro-burrs really aren't very controllable. One does everything correctly (I even use a lab microscope occasionally) and with some steels micro-burrs sort of flake off irrespective of the method of sharpening and or steeling them.

Some steels are just horrible and tempering and hardness are not necessarily good indicators of quality. I have a few chisels that superficially seem OK and the steel is hard and takes a good edge but five minutes later they're useless, others, sometimes even cheaper ones, turn out to be excellent.

As a techie who like playing with tech toys I thought of using a handheld x-ray fluorescence spectrometers like, say, this one: https://alloytester.com/xrf-steel-tester. There are any number of them around these days but they're expensive even to hire and I can't really justify one just to indulge my curiosity. However though, it would be really nice to go around testing everything that has an edge and logging its alloy properties against actual performance tests. Perhaps some day.

I couldn't care less about original parts (they're tools!)—so long as the tool works well (I don't for a moment consider myself a collector of old tools). That said, when making repairs I'll go to some trouble with old tools to match a tool with its 'correct' parts if possible (but ultimately it's a pragmatic decision—if I don't have the correct part I'll use wherever is to hand or what works best). By that I mean if it's possible to mate together a tool with parts from the same manufacturing source and same era then I'll do. For example, my No. 8 Stanley somehow lost it's lever cap during a move and I had access to several others that would fit but I selected one that came from the same factory and manufactured around the same time (in this instance the plane was of US manufacture/New Britain and made in 1933, so it received another lever cap from the same factory made in the same era (it was of the first generation to use the kidney-shaped slot for the cap's screw). I'm in Australia, so I had lever caps manufactured in the US, UK and here (including UK Record parts) to choose from. Nevertheless, it now has a plane iron of modern manufacture (but I've kept the original one and it's identified as belonging to said plane). There's also another reason to match parts which is that they usually fit better (leaving Bed Rock planes aside, I'm also of the opinion that the best consistent run of 'normal production' planes Stanley ever made came from its US plant and were manufactured between 1933 and about 1941 (the run came to an end when war regulations kiboshed the quality).

I do have a sense of history when it comes to these old hand-tools, my No. 8 is now 89 years old but it's not the oldest, that accolade goes to my No. 45† which dates from 1907. I'm of the opinion that we never actually own these objects, we're just their custodians for life—after all, my No. 8 is still in excellent condition (so are several others which are older), and if looked after with a little care, it'll still have several human lifetimes left in it after I'm gone. BTW, its original owner wrote his name on a piece of paper and dated it then put it in the space under the plane's tote (I'm now very curious to know who he was but I've really no idea). Anyway, that piece of paper stays with the plane (I've really no right to remove it).

Incidentally, I have a copy of Antique & Collectable Stanley Tools - A Guide to Identity & Value - 1996 edition by John Walker. You're likely already aware of it but in case you're not, it's an absolutely invaluable 880-plus page tome on the subject of Stanley tools, there's nothing else its equal. It's the ultimate bible for not only collectors but also for anyone who fixes or refurbishes these tools. There's a new edition out which I've not yet seen (it was out of print for quite some years which made secondhand copies of it much more valuable than many of the tools mentioned therein).

Back to plane irons, I use this mob from time to time for replacement irons but they're expensive here where I live. They are reasonably consistent and work reasonably well but I'm not altogether totally happy with them (it's what I now use in the No. 8, No. 4, 5 etc.): https://www.ibctools.ca/product-category/ibc-blades/. They'll also do paper-thin shavings but that's usually of secondary importance—for me, a steel that keeps a keen edge for the longest duration ranks first (these come close but I've had irons that cut somewhat better).

Thanks for your comment.

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† Damn monstrosity of a thing it is, the only thing I can imagine that's worse would be a No. 55.