Blank sheets of old paper in small sizes are still available in fairly large quantities. Larger sheets are also found though in much smaller numbers. From the late 1400's until about 1800 European paper was made from rags pulped in water. After about 1800 paper was increasingly produced mechanically from wood-based pulp, treated with chemicals. Even though the old paper animal glue may have deteriorated with time this paper is acknowledged to be tougher and longer-lasting than much of the 19th century paper.
Old paper is commonly of a heavy type, fairly coarse to the eye and to the touch.
When paper feels very smooth it is most likely of more recent origin. Bleaching of old maps can result in a pristine white paper colour, loss of original colouring, if any, but will not remove other tell-tale signs like tears, worm holes, thin spots, etc. Even when backed with Japan paper, this type of damage may still be visible, althought new techniques, including a machine which joins new paper to old sheets, are making detection difficult. When paper edges are like new, they could have been trimmed recently to make them more presentable or you may be looking at a modern reproduction. Some folded editions of many of the famous early atlases were made and maps have been sold separately as well.