Don't hold me on this but as far as I know, there was a picture of a brochure of DM53 posted sometime in the past on the net where it said the penetrator body was 685mm though I don't remember if it also said anything about the diameter;
Regardless of this, i think comparing DM53 to Type 10 AFPSDS is a bit of a moot point and it would do us better to compare DM53 to M829A1/2 which both have 680x22mm and 690x22mm penetrators respectively in a projectile body roughly ~760mm long (though it's 779mm long in total).
There's also the case of yet another, I believe Rheinmetall brochure from 2014 or so stating that the projectile body of DM53 is 745mm long (i'm assuming that they excluded the fins that extend beyond the body of the main body of the projectile.
I've done my own share of estimates on DM53 and 63 in my free time and this is what I had got:
Did an estimate for DM53 once again just a moment ago;
In regards to the DM63 estimate, since i already had numbers for diamater and the stuff, i just did a comparison of how long fins on the 53 and 63 are, substracted the difference and that's how i got to ~770mm total length and 745mm "effective projectile length" (or perhaps it could be called in-flight length?).
edit: just found this, i don't know where this comes from but the penetrator length matches what was said in the Brochure, diameter is a bit too high though it also matches if you count in the ribs which in my estimates were roughly 25.8mm
And overall i think this graphic is legit;
They all roughly fit with penetrator length, diameter is a bit iffy cause I dunno what kind of criteria they used for diameter there.