The diamond on texture of the two "sanding" bits is interesting. I wonder if sawdust would load up on the bit fast or not. My first impressions; "stone" it was for shaping rubbery textiles and diamond it was a coarse abrasive I'd use for fast dressing badly rusted steel, to ease starting welding arcs.
But lots of space between surface areas for heat to run to, and coarse enough to shed a rubber/plastic debris load too. If damp wood dust or aluminum loaded up on that, it would be bad.
Diamond?... For grinding glass?
Anyhow... I can't recall what came with what Exacto set anymore. This is just what was handy, there are many tools missing here too.
I do have those exact shankless saw blades. I never checked the mounting for notching with the other tools, but do think they are useable in exacto if you mind the teeth and collet tightness.
Exacto branding focus on the pen knife, has side stepped that there are actually a few BASIC handle shapes and, at least FIVE shank types. 1-Blade, 2-tube/shaft,3- half tube, 4-"V-notched" or "wing base" and 5- the hoop or "split tube". That's all I've ever known to call them. Never bought even one specialty blade, one of the bulk bought supplies now on thier 3rd generation of ownership seeing a fourth generation of use, lol.
I know there are also lots of other specialty tools they made, and bigger kits like this too. Many seldom imagined ones too (e.g. swivel tips, push button, fat pen, short pen, short fat pen; finger guard's, jigs, depth guides, etc.) This kit of my Grandfather's is the largest of the six kind of boxes I have now. Like with an interest in trains, my carvings ment folks that saw them wanted me to take their relatives sets. I actually only bought one red handle ever. This one is not the bigger than one monster box my Grandfather had at his shop though.
Usually it comes down to two basics. The "pen" handle; takes only flat blades that I know of, and the "tool handle" that takes them all.
I seem to recall smaller hoop blades too for pens too. But Exacto? That, I don't know.
On the fat handle Exactos (one of my old ones has the black teardrop handle too, this newer one is a different grade of aluminum :p , the hoop blade's 2 shanks fit in the outer twist-lock, wedging to/ wrapping around, the center jaws that can also hold flat blades and razor saws.
Left to right, This old knurled or notched, straight red handle's thinner twist lock shows decades of use with those. The newer (longer?) teardrop handle with blade (1)and thicker collet build. Tube/shank pull cut razor saw (2), leaf blade on a half moon shank (3), round hoop split shank (4), and 2 random V notch/ wing blades (type 5)
(I kept wanting write slingblade, lol..uh huh )
I never looked, but it wouldn't surprise me if there were square steps for thread taps inside the holes on some tool handles.