This is just something tongue-in-cheek, and meant in good fun, that I was writing some time ago about the different ways things can be historically incorrect at historical reenactments. My wife and I started out participating with a living history group that had a heavy educational goal and I eventually started writing this as a way to explain to novice reenactors that even though an artifact existed in the century you portray, it did necessarily mean that it is an appropriate accessory for a reenactor portraying that era.
Sub-Definitions of "That's not Period"
"Close, but wrong continent": Something that can clearly be documented during the time period, but comes from so far away geographically you have to create a unlikely story to explain it. -A Highlander carrying a Samurai's katana.
"Close, but wrong class": Something that was being made during the time, but was rare, or so expensive that it could only be afforded by the most wealthy individuals of the time.
"Name that Stereotype": Items that reflect the stereotyped "traditional" dress of a country. -Wearing modern kilts and the accompanying Victorian accoutrements in the Renaissance.
"Ancient History -when in Rome...": Something that went out of fashion so long ago it was unlikely to be seen outside of some nobleman's collection of antiquities.
Century-impaired (Era-impaired): Dressing historically accurate for one century and attending an event that portrays another century. An acquaintance described attending a Scottish fair, and watching a couple dressed in American Civil War clothing trying to "blend in" with a group of Highlanders.
"Gerry's not dead -I talk to him whenever I flashback!" Tie-dye, hippiewear, or anything that dates from the Nixon "reign".
"Frodo/Jack Sparrow Lives!" Swords, costumes or other accoutrements straight out of any popular fantasy or adventure movie.
"A Novel Approach to history" Your "documentation" for that comes from a work of fiction?!?
