I should have looked here first
https://doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=407364&page=all

Courtesy of SGL
Ideal barrels are dovetailed and cross pinned, the genuine Demibloc system as invented by Henri Pieper.

Robust Barrels are monobloc, with the barrels inserted and fretted into the monobloc (cannons en frette) ie held by friction as well as solder.

ROBUST_IDEAL is a kind of hybrid between the Robust and the Ideal, having monobloc barrels, but not the "T" top extension. The top extension is from the Robust, flat with a flat bite.

The stepped monobloc was abandoned in later production in the Robust in favor of faired barrels.

The Ideal in the late catalogs, just before 1982, is shown in two models, the Deluxe and Prestige with monobloc barrels, though I have never seen one yet. Even though I have seen and handled hundreds of them I have yet to see two identical Ideals or any with monobloc barrels. The custom capacity of the workshop must have been staggering.

https://sites.google.com/a/damascusknowledge.com/www/home