Sometimes an object does not fit. One or more of these methods suggests the object is older than it should be or is somewhere it should not be, if current theories are correct. Such an object is normally called an OOPART standing for Out Of Place Artefact, though the term can also be used for non-manufactured articles, since OOPOBJ is not as easy to say.
A lot of apparent OOPARTs have been found, but most can be explained without assuming they came from Atlantis or an extraterrestrial spacecraft. There are however a small number that pose a problem to conventional theories and are generally ignored because any archaeologist who investigates them is likely to suffer career damage. Even if this is not the case an academic archaeologist will generally have little time to research anomalies. As a result these objects have been appropriated by religious groups and other fringe elements as proof of their pet theories, without real investigation and ignoring the fact that weakening opposing theories does not mean their theory is right.
Ancient Machinery found in RussiaRecently there were claims of an ancient machine part being found in Russia generally  being lumped together with other OOPARTs, some of which may be fossils. One geologist considers it is either a natural crystal of Iron Pyrites or, since it was not discovered in the mine itself, a something that had broken off mining machinery. The argument they make that the fact it was not published in a peer reviewed journal is however weak: No journal would publish it until it was verified, and no mainstream scientist will try to verify it until it is published. This is a weak case and can safely be discarded.
The Crystal Skulls
There are a number of model human skulls carved in quartz alleged to be from pre-columbian South America. On investigation the problems with this interpretation seem to multiply. Not one of these skulls has been proven to be pre-columbian, and the best evidence seems to indicate they were carved in the 19th century in Europe. The most famous skull, the Mitchell-Hedges skull was purchased by Mitchell-Hedges from a London Art dealer in 1944, though his daughter claimed have found it during an excavation. The skull seems most likely to be a copy of a 19th century skull in the British Museum. Whether or not they are ancient they are remarkable sculptures doubtless attractive to those who are attracted to skulls.
Regardless of scientific evidence many paranormal claims have been made for the 13 or so known skulls which can kill at a distance or cure cancer. Claims of skull-lore and mythology seem not to have existed in Ancient South America and any ancient South American myths seem to have been spread initially by Mitchell-Hedges and taken up by New-Age writers who considered them as relics of Atlantis.
The fact that the skulls are 19th century does not preclude the possibility they now have some paranormal attributes for belief can do remarkable things.
Criteria for real OOPARTs
- have an unexpected age (too old or too young),
- be in the wrong place (Roman artefacts from Mexican sites),
- have an unknown or contested use,
- be of anomalous size or scale,
- have a composition impossible with current understanding of ancient technology (aluminium in ancient China),
- possess a sophistication not commensurate with those models (electric cells in ancient Parthia),
- or have unexpected possible associations (mylodon bones from Argentinean caves suggestive of domestication by humans).
It must :
When evaluating a possible OOPART you should ask at least one question for each criterion, for example
Is the date reliable?
Could it have got their through trade or been moved down by earthworms or earthquakes?
Can you see a possible use for it consistent with the known level of technology?
Could the giant/miniature object have been something else or used for rituals?
Is its composition really anomalous?
Was it really found with the other articles mentioned?
One final criteria not on Corliss' list is:
The trail should not go cold
The object should exist and be potentially open to further study. If it has vanished then the assessment must be made on circumstantial evidence. The fact an object has vanished does not mean it never existed: museums tend to put anomalous objects first in storage then in the rubbish. Even if not deliberately discarded accidents happen. An example where the trail is almost cold is the Dashka Stone  which is apparently on exhibition in a museum, but where the original discoverer , who gained points for being a respected physicist, seems first to have become an uncritical believer in ET intervention, then vanished from the face of the earth. A cold trail is a warning sign not an indication the object is not anomalous.
Unfortunately almost all alleged OOPARTS seem either to vanish or be unable to withstand investigation.
 http://www.badarchaeology.com/ Bad Archaeology
 http://alexk2009.hubpages.com/_aayawa/hub/Mysteries-of-the-Map-of-the-maker The Dashka Stone
 http://doubtfulnews.com/2013/01/come-on-russian-media-a-ufo-tooth-wheel-silly/ Skeptical take on the Ancient Machinery found in Russia
 Lost Civilisations of the Stone Age: Richard Rudgley.