NOS stands for "New Old Stock." When a watch is described as in NOS condition, it refers to a timepiece that was probably put away for decades and has never been worn. However, over the years, it may have been passed from one collector to another, but as long as the new owner keeps it unworn, it can continue to be described as NOS. It may have been tried on just like those display pieces in a watch shop. But one thing is for sure is that a NOS watch is not mint. Most have been put away without protection (such as inside their original box), so expect the case and crystal to show minor light scratches here and there. Some will naturally patina or produce age spots depending on the dial material or type of luminous/paint applied on the dial and hands. But, at the end of the day, a NOS watch's condition will differ from a used piece in pristine condition or a timepiece with a case polish. A long-time collector will be able to differentiate them apart.
 
Here is an attractive vintage NOS Tissot watch. Factory original Arabic luminous dial with some aging. Luminous burns are common when an old watch rests in the same position for a long time—fully serviced Tissot calibre 27B-1 manual wind movement with serial number 2803782, dating this timepiece to 1952. Unfortunately, the original crystal had internal acrylic stress marks and had to be replaced with a new crystal. Depending on how tightly an acrylic crystal is installed onto the case, over time, the crystal may begin to produce these stress marks, which show clearly, especially under the sun. This model originally came with an unsigned crown. The case is made of solid stainless steel and remains in excellent condition. But this piece most likely may have been put away in a watch shop drawer mixed with other things, which is why the case does show quite a bit of light scratches. The case model is 6787/6788-4 and measures 33mm in diameter, excluding the crown by 41.8mm from lug tip to lug tip. Original metal case gasket and sticker. It will come with a brand new 16mm genuine leather strap. The wrist size in the photo is 6 inches.