This is not an old style pot but just a screw lid instead of the lid on tins of enamel paints which have to be opened with a screwdriver.
There is usually a selophane wrapping over the etire bottle when you buy it which must be removed. Then its just a case of cutting any stickers which are spanning the lid and the body of the bottle.
I dont usually have a problem with the paint drying and sticking the bottle shut around the seam of the lid but i imagine that if you held the bottle in a towel of warm water then it may do the trick.
Hope some of this helps,