Just after some info on the old Ducon Condenser is the end with a black band around it negative ?

Just read an article the black band just means lower voltage on that side and has foil on that end

As noone else has responded I'll make my first post trying to help.
The general answer is yes but that's not really true, Polarised capacitors (electrolytics and others) must be put in the right way round or they may blow up.

Non-polarised film capacitors, and most likely the sort you are asking about, used to have a ring around one end and in most cases is the end connected to earth - nominally the negative return for the B+ supply.

The end with the ring identifies the end connected to the last wrap of the internal foil and the circuit and not the capacitor can benefit from this end being connected to earth by offering better shielding to the capacitor.

Modern film capacitors don't usually bother to tell us which end is which. There are many ways to discover the outside foil end if you want to know.

Cheers
Thank You

More precisely, the outside foil end should be connected to the side of the circuit with the lowest impedance, which is earth when the cap is connected to earth/chassis in bypass mode, but take note of how original stage coupling caps are installed if you want to be 'religious' about this.

Those are normally referred to as outside foil. As noted the band is the earthy end. This tended to act as a shield and you can have the odd issue, mainly in the second detector first audio area: This tends to be a problem area.

Also as noted the modern caps are not marked outside foil. As all of those capacitors and several others, like a white UCC (Hi seal) with a plastic jacket are waxed paper, their destination is the bin. I had Kriesler 11-81A come in today & its full of them. It wont be when it leaves.

Normally by now they all leak electrically & the coupling ones especially, if measured at less than 200Meg with an insulation tester are duds. My spec is if it leaks at all its a dud. Testing them here is considered time wasting as it has proven in around 50 years, not worth the effort of finding a very rare, good one.