I enjoyed looking at your notes on the AKAs as well as the Prominent piece. The german journal Photo-deal number IV 2018 has an article on the AKAs which may be of interest. As for the old Prominent compurs, mine does open but not fully, so I expect the oil has dried out. Luckily it is totally distint from the glass, so I can try the normally very unsafe and temporary method of a drop of penertarting oil. Anyone tempted to aquire a prominent with the nokton 1,4 should look closely at separation signs at the edges, mine is OK,but I expect that high temperatures and rapid temperature variations should be avoided. The Ultrons i have seen of this vintage have not suffered.
p.