[Username1]

Brandersen is right, the marked end is the outside foil end. It was thought that that side should be the grounded side if it were going to ground, and in that way keep noise down. But if you unwind one, you find the outside foil is only exposed to any outside potential noise for just the first 1/2 inch of the winding. Most likely your new cap has no outside foil marking. Radiotvnut is also right, in older sets electrolytics tend to be phisically larger than all other caps you see, so Identifying them in older tube sets is a little easier, and there is a polarity marking in them, not just a stripe around one end. If you have a schematic for the set you are working on, they are marked as polarized on the diagram.